The feedback argument makes no sense. User ads disappear immediately after they are marked "Sold." If anything, user ads should stay up for a little while - but sponsors are known quantities. So why would we care if their stuff goes bye-bye?
The other thing is that sponsor ads seem to rotate, which means that all these sold items choke out or obscure the things that are actually for sale. That's not helpful.
Also, sometimes when people are hung up on price histories, they want to use that as an excuse (to sellers) for why they should pay 2010 used prices for an Xpan in 2018, for example. The market price of something is what a buyer and a seller agree on at the time of sale (unless principles of micro econ have changed), not what someone sold to someone else under unknown conditions years ago.
If you want price history for cleared sales, the auction site has plenty, with better sample sizes, far more searchably than here.
D