Had never really thought about it in those terms, but yes, just as a green seems to need at least 6 (and for busy public courses, maybe up to 21) reasonably level (usually defined as less than 3%) to set cups, there is no doubt that golfers will find the level spots on the tees. If a course needs 6,000 SF of tee (based on "industry standard" of 1.5-2 SF of tee per 100 rounds) then sure, add some rolls, but be sure to leave that 6,000 SF level. Any golfer seeks to take advantage of everything he/she can to improve their score. Only a gca nerd would play off a non-level lie just for the fun of it. Since there only seem to be 1400 of us here, the sloped areas would get a small fraction of play, unless the tee markers were set only there.
I do know a few tour pros (and presumably more low handicappers who think the same way) who think the 1% slope of a normal tee ought to consider their shots, i.e., if they want a low shot, slope tees to the front, high shot, to the back, hook, slope left, fade, slope right. But there are other factors that often override that gca's normally consider first, i.e., drainage away from path, drainage to low side (i.e., slope to front on tees sitting on a downhill slope, etc.)
Let's face it, the tee shot starts the hole. The idea of playing it how it lies is generally reserved for second and subsequent shots. It has been established by consensus that most golfers like the idea of starting the hole on level ground. And, in reality, gca isn't about raising the scores of players, it's about letting them have a reasonable (not guaranteed) chance of hitting successful shots, with perhaps one shot type, pattern, height, etc., slightly favored that allows them a better score, not reducing their chance of success by design.