My flat bar group doesn't use gels, hardly surprising since the idea is to ride without knocking yourself out.
However, our experienced leader said the same the same as
@Blue Hills - a gel can have its uses in getting you the last few miles if you are really cream crackered.
I was given three or four years ago which will likely now be 'expired' by several years.
I'm grateful to
@Blue Hills for being a bad guts test dummy, so might put one in my trunk bag before the next long ride.
On a separate note, a now deceased member got into bother during a hilly tour in Northumberland.
He made himself properly ill by eating several gels in an attempt to complete that day's route.
Seems to me the moral of that story is if one or at most two gels don't do it, find another way.