I used to pre-order games, when physical copies were the only copies of games. It was inevitable that stores wouldn't get enough supply to meet the demand for big releases, and I wanted to ensure a copy on release day. Made sense back then.
I also used to pre-order games if they had something cool as a pre-order bonus. Best Buy in particular used to give out nifty stuff for pre-orders like t-shirts. I still have t-shirts for Max Payne 2, Deus Ex: Invisible War, and a few other games that I got as bonuses from them.
The thing is, though... back then, pre-ordering a game was just $5. These days it should be called pre-buying. Back then, I could put $5, then pay the rest upon release. If it turns out the game is a flop, I'd only have to eat a $5 loss - no biggie - and I'd get to keep all the stuff that came in the pre-order bonus package. Hell, you could have probably made back the $5 loss by selling the pre-order stuff on E-Bay or whatever back then. I'm sure someone out there would have paid $5 for a Max Payne 2 shirt.
These days I rarely pre-order, since I don't like the idea of pre-buying. I still do it from time to time, but I restrict it to releases that I'm fairly certain of the quality. Despite my massive fanboyism toward the Aliens series, I didn't pre-buy A:CM. I did, however, put money down on a copy of StarCraft 2: Heart of the Swarm because I'm fairly certain of what level of quality I can expect. I try to choose it on a case-by-case basis, rather than just pre-ordering/buying everything I'm interested in. It would take some seriously awesome pre-order/buy bonuses to get me to go that route. Bonuses that are unlikely to exist, 'cause it's the t-shirts and stuff from the 90's/early 00's that I personally miss.