Mailanka has expanded on his post about loot and gear, and I recommend reading it.
I like the idea of abstract wealth for many games - it takes the day-to-day financing out of the game and makes it about choosing stuff, accessing stuff, and doing stuff - not about the nitty gritty of detailed equipment tracking.
Oddly enough, then, the game I play in - GT - and the one I run - DF - are all about nitty gritty details like coin weight, bullet counts, gear shopping, and so on.
Like Mailanka says in his post, some games are about that directly. Counting rounds after the apocalypse is part of the fun.
Looting orcs for every last coin and searching the stomachs of giant frogs for swallowed gemstones is classic fantasy gaming.
The detail is a strong and important aspect of play. James Bond doesn't fret about where he gets gas for his car but Mad Max sure does. Conan squanders jewels in the fleshpots of the south, but PCs in games want to hoard every coin until they have enough for . . . whatever. Magics swords, potions, castles, henchmen - they cost, and a few gp here or there can add up.
This is why I track equipment so closely in DF and why we do so in GT.
It's also why we track the details of gear so closely. It is, again, part of the fun and the challenge.
It's really something well-supported in the game system and part of the genre.
If I ever do get around to running a modern game, I'll use abstract wealth. It's just easier to roll and see if you can buy, or just have, some random stuff than have people tracking dollars and cents and going on Amazon.com to check and see how much one of those costs. As easy as that is, and as convenient, tracking it all is likely to take away from the game.