The 22 LR round has a heeled bullet, the front half of the bullet is the same diameter as the case and there would be nothing for the case to head space on. You need the rim.
Imagine the manufacturers dilemma, do they make the case diameter larger making all the chambers of all 22 rifles and pistols useless or reduce the size of the bullet making all the barrels chambered for the 22 useless. There there is the matter of rebating the case to allow an extractor to grab the 22 case for removal and it just gets more fun from there. Sometimes it is better to let a proven product that is still doing the job for which it was designed and does it very well to just be. I'd be ticked if I couldn't find ammo for my 22's anymore and even more ticked if I had to re-chamber or re-barrel 12 of my guns in order to shoot a new round which would undoubtedly be much more expensive and not any better than what we have.
Good intentions will always be pleaded for any assumption of power. The Constitution was made to guard the people against the dangers of good intentions. There are men in all ages who mean to govern will, but they mean to govern. They promise to be good masters, but they mean to be masters.