Mexican restaurants and bland food.

Why is it that every Mexican restaurant serves food that is so damn mild?
Okay, maybe not every one but most that I have visited.
Richardsons in Phoenix knows how to make a spicy meal.
I've tried the corporate places....El Torito, Chevy's, Garcias...I have tried independents, almost all of the time that I ask them to spice it up, they mumble some bullshit about how they can't do it.
Why? Do all of these places buy prepackaged meals from one source and just heat it up?
I love a spicy meal. I am 99% white but I have always liked the stuff.
Do you think that these places are just playing it safe to avoid turning off customers? Are they just playing to their average customers that can't handle it?
You'd think that a guy in California could get a decent Chimichanga or enchilada.
Do I need to go to Texas to get a decent meal?