I am 55 and I think the biggest issue we weekend warriors have is just that we are just simply getting older. The music changes and the venues change. So we are not willing to change (keep up?) and don't have the passion, maybe. We have other interests (children, grandchildren, other hobbies, careers, etc. etc.). We don't like the change in music. My journal of part time gigs was full from age 16 until about 40+. One or two nights a week.
On the other hand, my friends who are 35-40 years old are busy as ants. So are the few guys older than me who are willing to work at finding gigs and adapt to other music! And they are making decent money.
A cabinet maker who always did formica tops and refuses to do granite or corian (sp?) probably is on a going out of business plan.