source engine is different from goldsrc, and the "feel" of goldsrc goes back to q2 (and some idiosyncrasies from q1). so if you spent several years playing from beta days, or for some people transitioned into cs from even more years of q2 or q1, then source would just be an entirely new experience. there's nothing valve could've done to preserve the right feeling, which is fine. old timers continued playing goldsrc until full blown grown up took over, where's new timers were formed by the conventions of source and further.