I like it because it doesnt involve a man.
Its not a homophobic thing; its often more sensual and even when using a strapon its not just mindless pounding (mostly).
Even though Im.. 'sexually experimental' I often find men in porn to be grotesque and plain disgusting.
Of course, seeing two women at once is also a turn on, but I also enjoy the fact that no one is necessarily submissive to another.
There is, of course, dominating and submissive roles in lesbian porn as well, but its often considered a overly dominating/submissive porno, whereas in straight porn men naturally assumes a more dominating role, just like women usually assumes a more submissive role.
These are just my personal thoughts, I seriously thought most men think too much about it.
So for me it mostly comes down to that they are more sensual and I dont have to look a another man.
I could ramble on but this is already too long.