A good friend of mine in the hobby, began in the hobby as a kid in the late 90's , with a great eye to spot the rare card accidentally put into in the 10 cent and 25 cent box at the LCS. He'd spend hours in that box, pulling 4 cards for $1, that he didn't need, he simply knew their value, and then flipping them for 4x $10 cards he needded for his collection. I never had the patience for it.
As time went on, he began spending his time at shows doing this, and selling his finds on ebay. Using the ebay profit, to buy a card on ebay for his collection. As time went on, he graduated to searching the $1 box at shows. He became obsessed with his ebay feedback score. He spent a lot of time on his listings, trying to give the best description of condition.
He claimed that about 1 in 10 buyers had buyers regret of some kind and asked to return a card. He was afraid to say no, because of that obsession with feedback, and also, ebay and paypal are 100% in favor of buyers on all complaints. Trying to dispute a buyer claim, and request for refund, is almost impossible. This part of the hobby gave him ulcers.
About 2 years ago, my friend who never sent cards for grading, now no longer a kid, flipped his model of the hobby to grading everything he wanted to sell on ebay. The bottom line, he's selling a PSA 9 of card XYZ, or selling a BGS 8 of card ABC, and there is no longer the need to describe the card condition on ebay. No longer any dispute with buyers. No longer the potential for buyer to complaint to ebay - card not as described.
It reminds me of the begining days of ebay, when cards were sent through USPS regular mail, and 1 in 10 would complain that they never recieved their purchase and demand a refund. [half lieing, and the other half impatient when it didn't arrive within a week of purchase] The hobby quickly adapted to adding tracking on postage, and signature verification for a high end item, and pass throught of the cost to the buyer.
Anyhow, I don't collect graded, just sharing a story of why it works for one guy in the hobby.
"Ability may get you to the top, but it takes character to keep you there." - John Wooden