There's probably many reasons for the lack of attendance.
For some people, the whole bowl/gong "sound bath" thing may be a fad and that fad is already beginning to wear thin.
For others, there has been so much marketing of bowls and gongs in recent years that many people now have their own.
Then there's the reality that many of these new "practitioners" are really novices without much depth of experience,
skill or insight into what they are doing, thus rendering the experience shallow and leaving many people with a limited
view of what the experience has to offer.
And then there's all of the other experiences of contemporary life that seems to have so many people commited to
an endless string of activities of all sorts with little time to breathe and rest. As you said, "more people, more stress"
which may translate into "less time" for bowl meditations.
I've been involved in this work for several decades... long before it became a fashionable trend, and what I do is far
more than a bowl meditation or a sound bath. Sometimes I get 30 - 50 people attending and sometimes events are
cancelled for lack of interest. Usually interest falls somewhere between those extremes. (And there's a certain setting
where I've been getting 80 - 100 people several times a year.)
We must remember that even as a currently "fashionable trend", it remains so for a relatively small percentage of the greater population.
And then, who knows.... my reasons stated above are just a few ideas - I hardly have all of the answers!