The responses here are good ones to an equally good question.
Tuning down is often considered to have many benefits
I can add this:
Sometimes players tune down to take some tension off the neck. This is especially true if heavier strings are used (higher gauge equals more tension), or on 12-strings (more strings equal more tension).
As you go lower, heavier strings tend to "tune up" better. On a decent acoustic (& often electric), you can tune "standard" tuning down as much as 2 whole steps (Elizabeth Cotton & probably many other folk/blues players; popular today with heavy rock players).
Don't expect the intonation to be great. Think about how much longer a bass neck is than a guitar's. 2 whole steps is a third of the way to the bass' register, so a standard guitar neck is a bit out of scale.
LH: I also find the lower keys easier to sing many songs in. I'm seriously considering a baritone guitar. I've played a few; they sound huge & happen to fit my vocal range for songs I need to play in a given position on the guitar.
Regards,
CC