Bear in mind I am no musicologist. My knowledge of musical/cultural history is rudimentary at best and perfunctory at worst. This is a complex question with very many components to it. I'm offering only a small look into the ways singing has been perceived through the centuries. https://twitter.com/DescantCantus/status/1296258845476446209

As a member of the Western musical tradition, this discussion will focus only on the Western musical tradition. That is, music born from Europe, European immigrants, African slaves in the U.S. and black Americans.

Why do most people have the capability of singing, but only a few can sing really well? The answer to this question depends on who you ask. Some argue that singing is a gift that is divine in nature. Either you have it or you don't. Others argue it's a skill that can he honed.

Historically speaking, singing has been a significant part of humanity since the beginning. Cultures from every part of the world have developed their own musical styles and traditions. Many of these traditions are still alive today.

We must make a distinction between music of the oral tradition/performance and music as an interpretative art. The former has been a staple of ancient societies. The latter is relatively recent and is a major component for the development of the Audience vs. The performer.

In ancient Greek society, everyone was taught performance mastery. Everyone could sing and play instruments quite well. After the fall of the Greeks, the Romans took on many of their musical traditions and disseminated them into the masses.

After the fall of Rome, you have the Roman Catholic Christian church. It is here that the gregorian or plainchant was born. A form of worship music, this was performed in the church by the congregation. From the congregation there arose a "choir". Select singers to perform music.

Women were excluded, unison singing was transformed, and instruments weren't allowed. This provided a stark contrast to music outside the Church.
However, the church's influence would fall and more secular musical traditions would take root.

With the advent of widespread musical printing in the 15th century, music became more easily accessible which further shaped performance traditions.
Remember audience vs. performer? That shift occurred most clearly during the 17th century with a change in the term "virtuoso".

In modern times, a virtuoso is someone who has technical mastery in a particular art, like singing.
With the advent of Opera during this time, the technical difficulty of music increased, thus leaving a wider margin between the performer and the audience.

Now you have a clear difference between a (skilled) singer and the masses.
With this difference there comes a change in general perception as to who should or would engage with music on a higher level.

Make no mistake, the idea of performers and soloists have existed for a very long time. But the delineation between average and gifted is what we want to observe.
So, consider- From community singing unison(one part) to a special group singing, to harder music being composed.

Keep in mind, poverty, lack of access to musical texts, musical illiteracy, and lack of formal music education if you weren't in the church, at a singing school, or of the aristocracy.

Thus, it became more and more common for the public to leave "good" singing to the professionals

In the U.S., slaves crafted what's now called the Negro spiritual. Communal singing that was very much a part of life. After the abolition of slavery, there was a boom in black musical forms. Ragtime, Jazz, Blues, Gospel, boogie woogie, etc.

The performance tradition shaped even these forms, giving birth to high level and virtuosic performers alike.
The audience can relate but perhaps not replicate.

With high level performances comes a certain perception. The belief held that singing is something given--not developed. With the lack of musical education formal or otherwise, more and more people buy into this belief. They aren't inspired to do better because they "can't."

The Audience vs. Performer paradigm has cemented itself into our cultural psychology. What was once mostly communal and even commonly mastered, has since become an art that is reserved for the few willing to undertake it.

Throughout history, there are probably millions of people(famous and otherwise) who could and can sing well. If you ask me, the only difference between a good singer and a bad singer is a belief and *effective* practice.

Alas, the aim of this thread wasn't to tell you how to think. It was merely to provide context to the question posed above. Of course, it is my belief that anyone has the opportunity to sing *well* provided they have a working vocal and auditory apparatus.

Anywho TL;DR
Everyone at one point sang
Lot of folks sang good together
Church said choir boys only
Church fumbles
Staff paper available in a store near you
People said we want SANGERS
People stopped believing they could sing well
Present day world

Thanks for reading this far. I'm no expert by any means. Just a simple music educator who believes in the transformative power of music. Have a great day!