I for one use standard E most of the times when I play guitar.
The reasons are:
-I'm too lazy to tune around all the time
-I like to play with thin strings because I feel more comfortable when gripping them, so they wouldn't be tight enough anymore if I tune them 2 steps down for example
-It doesn't make such a difference to me if the song is a bit lower or higher. For me the tunes and riffs make them sound good or hard or whatever you want, not if the lowest note is c or e(although I like c minor a lot and with the piano when I don't have to tune down anything I always choose c-minor for writing some songs ^^). Don't get me wrong, I like low tunings but not as much that they could overwhelm my laziness and my need for comfort when playing.
If I play In Flames who use dropped bB I simply use dropped D, for I don't have to tune my guitar too far down and I can use the same tabs still for the harmonies are the same. (Don't know if I explained this well. Did you understand what I mean? ) This way of course I can't play along with the songs, but well, as I said before...my strings are too thin to tune them down 2 or 3 steps. Maybe I'll once have the money to buy a second guitar and then I would put other strings to that one (or buy a seven-string), so that I could also play in other tuning which I would sometimes like.
If I play bass and cover some songs I always use the tuning the band who made the song uses because for playing a rhythm instrument you need to play along with the rest of the music in my opinion. I for one would consider it as completely boring just to play with the bass and just hear the notes the bass plays without the real tune of the song which is given by the guitars and the vocals. So as I'm forced to use the same tonality then I tune my bass down no matter how loose the strings get LOL. Sometimes that's a problem. for example when I played Cradle of Filth - Her Ghost in the Fog. It's usually played on a five or six string, I don't know, but there is a B-string for sure. As I only have 4 I had to tune the E down to B which caused a real strange feeling of playing