Why do you use the tuning that you use?

I keep my own guitar set to D standard. I like the added depth I get from this, and it allows for a variety of styles. I'll flip it into drop C every so often so this allows for a variety of styles for me to play. I mostly play power metal and I like the ballsier attack I get. My band also plays in D standard and even though I'm not the guitarist, I write most of the material on guitar so having one in our tuning helps. My band plays in D standard because it heavies up our tone, and D is a good key for me to sing in.
 
The last band I was in played solely in C-standard tuning, so that's what I was tuned to for quite a while. I actually tuned my 6-string bass up a half-step from standard tuning instead of tuning it down 2 whole steps as the strings would have nearly fallen off, haha.

Right now I'm usually in E-standard for my project This White Mountain, though one song was written in dropped-A# because I happened to be tuned in C-standard and needed a drop tuning to finger the chords properly (no, not power chords, I'm not that poor of a musician).
As far as everything else goes, I'm usually in C-standard tuning, though I will switch it on occasion if I'm playing along with another song and I don't feel like playing along to Guitar Pro.
There's really no reason for me tuning to C-standard as opposed to say, D-standard, it's just what I'm used to. E-standard, however, is too high, IMO, for heavier stuff.
 
drop A#, cus its brutal as fuck.
my band WAS gonna play in drop A but the other guitarist was like"my strings are too l00se"
 
I use a lot, depends by the song and the singer but usually in D Standard.
 
If anyone spots any mistakes. Please point them out.

Well, you misspelled guitar, there's no verb in your second to last sentence, and there's an unexplained pronoun in the last one, although I imagine this is because you intended to use a comma instead of a period.:p
 
seven strings bass, recently tuned in E0(20,60Hz) all in fourths to fit the standard D2 guitar tuning my band use to get a thicker tone than their previous E2 and Eb2 standards

I prefer standard F#0 to play on my own