Sure, it's not that hard but it's time consuming service wise. When I serve, I have 30-40 covers when it's busy. So when I have to spend extra splitting up 8 checks for 25% of my covers, it hurts service. Our systems are easier for a bunch of single checks on bars (use a tab system) rather than table service. And you just don't hit a few keys once, you have to spit them all, click on each one to print, then when the cards come back, you have to select each one, run the card - wait for it to process and repeat - and when they finish, you have to enter the tip amount in each check before you close out the check for the next table that is sat.
The question is, how long do you expect to wait for a server to return with something simple? An extra napkin - but I have to ring in eight cards that will take 2 minutes no matter haw fast I go. So that customer is just going to be waiting extra long - 1 card takes 15 seconds.
Yes, some POS systems are much better but not every restaurant has a good system. Most still run Windows XP Embedded...