Transactions done up to today are only the beginning. Are we really going to drag around 2, 3, 4... years of transactions? WHY?
Because my coins are there, and I really want to keep them. I don't want my coins to evaporate because you can't spare a little hard drive space. What sort of crap system do you have? Even my phone can run a Bitcoin client just fine.
I guess "balance" and full "tx history" are two concepts to alien and complicated for you to grasp. LOL