At TXKF you'll be talking to the same controller from the time tower switches you until you exit the radar service area 180NM away. That being said, the controller has your route, cleared altitude, requested altitude, type, and probably any other pertinent information before you even enter the runway. Additionally we have an altitude readout on the scope (the purpose of you stating your altitude is for positive radar identification). The likelihood of confusing "for three-thousand" and "four-three-thousand" is extremely low. Excess verbiage is the enemy on a congested frequency, but if the controller has time to give you a lecture about your phraseology, than s/he probably isn't that busy.
I hear "for" instead of "climbing" a lot, from pilots and controllers alike, and I never thought anything of it until it was brought up here, and have changed my routine as a student pilot because of it.
The biggest thing really is the CYA factor. No one wants to sit on a witness stand in court after an incident and explain why they said something when the book says it should be said a different way.