@TeaKayB Your point is exactly on the nose. The attitude from establishments like this is often "You should be honoured we asked you", to which I always ask: "Why?"
They then often talk about exposure, and the like, and I drill down and point out the fallacies, just as you have here.
It can look good on the CV: "I was invited to speak at X, Y, and Z" ... and sometimes I'm asked to provide such evidence[0]. On those occasions I usually say "Go Fish".[1]
But some of the people in the audiences at such establishments have come back to me, ten or more years later, to say "I remember you speaking for my school/club/whatever ... will you come and do a gig for us?"
There is a genuine networking effect, and it tends only to happen via those "more prestigious schools", because socio-economics being what they are[2], they are the people who tend to end up in positions of influence.
But I don't care much about that effect any more.
I do care about having a positive effect on the students.
[0] Yes, really
[1] No, not really. But sort of.
[2] Unpleasant, but a fact.
CC: @icecolbeveridge @Martin_Whitworth @virtuosew