The rational is simple enough. Even though 128k is bigger than ever, it's not infinite. Optimization controls that are "standard" aren't as useful as optimization controls that fit the demands of second life. Optimizations that reduce code footprint (e.g. aggressive constant folding) should be usable without triggering optimizations that increase code size in the name of performance. I don't know what optimizations are available, and how you want to treat optimization control in scripts, but it seems that tailoring them to fit second life make sense.
