Why is it that classical composers stopped writing music for plucked strings?

Could it possibly have something to do with what I said about the linkage between high-art music and the role of the social classes during different musical epochs on that other thread?

I don't know the answer, I just make stuff up, like this:

In the 19th century, all of the baroque violins had their necks lengthened and reset at a different angle so the bridge could be higher and the strings more taut. This was done to make the violin louder. Other instruments went through similar changes--the pianoforte and the wind instruments--they all got louder. And the orchestras got bigger and bigger--instead of 12 or 20 instruments they grew to 50-100. Orchestras got way loud.

Why so big and loud? In the baroque period, orchestras were part of an aristocrat's household. Genteel folk would have one for private gatherings. So, when people went to a concert they were going to someone's house. So orchestras didn't have to be big and loud in the 17th-18th centuries.

Who were the big loud 19th-century orchestras for? Vulgar bourgeois riff-raff. There got to be so many of them, big concert halls had to be built to meet the demand. They would never have been invited to a quality person's house, after all.

So, try putting a mandolin soloist in front of a 19th century orchestra. You wouldn't even hear a faint plinckety-plinck. Thus, the demise of the mandolin concerto was inevitable.

One solution is to eliminate the fiddles entirely, but those 16-string mandolins need to be tuned constantly.