Why are they so popular? The couple of times I've used them, they've taken FOREVER. Wouldn't downloading straight from a server be much quicker? I mean I guess if you have a bunch of people seeding, then yeah, it'd be really quick. All I've ever gotten though was just like 2 people at it takes a couple days.
You basically answered your own question. Torrents are capable of being way faster than single-server downloads because of peer to peer sharing. When choosing a torrent, you should always pick the one with the most seeders, to make it worth it. Also, a lot of people download illegal things through torrents, and don't have the choice of downloading straight from a server.
Since when do servers have unlimited bandwidth? And since when do they have an uncapped upload speed? Think about it. 100 people downloading a single file from a single server. Not a chance you'll be getting your full internet speed like you would be if you were on a torrent with at least one fast peer.