I think they look nice sometimes in slabs and the protection is great for klutzy collectors like me. I had three rather delicate tickets that I needed in nice stable holders so I sent them in on the PSA March special. I hope to have them back in time to take to the National
. Same with all sorts of paper ephemera. Like this die-cut Benny Leonard that is now in an SGC case:
No way was I leaving that one raw in my hands!
Buying is less of an issue for me because the ones I collect [boxing, mostly] are not valuable enough that there has been a counterfeiting problem. Still, a slab does help me feel safer to purchase from a random venue like eBay.
As for resale, I think it depends. When it comes to resale through auctioneers, slabbing may save some money in the long run. Most AH's will give me a 0% commission deal on slabbed items but will hit me for 5%-10% on raw items [value and rarity dependent, of course]. A $100 ticket may not be slabworthy but a $300 one might make sense. I also tend to think that the slab will attract impulse purchasers. For example, a while ago I purchased a rare ticket that I stumbled across at a show. I was able to handle it and verify the security features and stock, so I knew it was 100% legit. I would probably have passed on it had I seen it on eBay raw at the same price.