In another thread, Jay Babina said:

Most kayakers care about their fitness and lifting and lugging your boat is part of it as much as paddling.

I've struggled to explain why some of my more 'rugged' and 'solidly built' boats are desirable. (The 'just another layer of glass' syndrome...)
I will definitely add that thought from Jay to my sales pitch! :-)

Seriously, it is a bit silly how many folks want a 30 lb boat that they can also drag up the beach when loaded with gear, bang into rocks, etc...