this is REALLY simple--i can't do lipslides on street. when i was a kid i'd always break boards trying them, so i never learned. nollie lips, etc, are a different story, but regular lipslides, frontside and backside, are the death of me. every once in a while i'll want to try to learn them, but i never end up trying.
i feel like i'm at a point in my life where i don't try to learn anything new--it's more fun just to do the tricks i know how to do, and cruise. i got really hurt last year--i broke my pelvis--and though i'm technically 100%, i still take an incredibly long time to warm up, i'm still really stiff, and i've definitely regressed skill-wise (street, not tranny. i'm fine on a ramp.). so, before the accident, where i'd do a kickflip back tail, i'm definitely happy with a regular back tail now.
what i'm trying to say is that the simple tricks i never learned--lipslides, frontside flips, noseblunts--i don't plan on learning any time soon.