I am a 'Sound Engineer' for my 'day job', and also a musican/singer.

My own preference is to perform without any electronic assistance, and I have sufficient audience skills to carry it off most of the time.

One factor that plays a part is the mental attitude of the audience. If you are playing a gig where people are paying specifically for the gig because they are interested, it is usually easier because they want to listen.

However, where the actual performance is secondary to making a collection for charity, you will often find there is a nucleus of people who have no interest in the gig and will talk quite loudly through it, oblivious of the fact that they are spoiling it for the majority. In cases like this I would use a sound system rather than risk ill-feeling... trying to shame people into behaving is rarely worth the effort!

Voice projection is an art that many people do not take the trouble to learn nowadays, but I learned the hard way in the late 1960s when sound systems were not the norm for stage productions. I was chosen to play a principal part in the college operetta (G&S Princess Ida), and the theatre was a 400 seater with plush furnishings - and there was a 16 piece orchestra, too.

Fortunately I'd been in the school choir from age 11, and had been taught the basics, but singing solo is far different from singing as a soloist.

As most people have already commented in one way or another, the problem is mostly down to people having lost the art of listening, and claim they 'cannot hear' unless you turn up the volume so their ears bleed...!!

But there is another issue...

Modern buildings are often 'dead' acoustically, so sound doesn't carry too well.

On the other hand, if you play in an older building you may well find that setting up a PA sytem is more difficult because of the natural reverb in the room...

It's a funny old world!