Im my opinion, a better question would be, why don't we abolish tipping, and let the restaurants, hotels, etc. simply pay their staff a livable wage?
It would make no difference in the final out-of-pocket cost to the customers--whether they have to figure out the amount of a tip, and pay that on top of the bill, or whether the prices go up to cover a proper wage, it's all the same in the end.
I do tip, but I base it less on the amount of the bill than upon the type of service I have received. If the server went over-and-above, yes, they will be very pleased with their tip. If, however, they did nothing more than take my order, and let it be served to me by a busser or some other staffer, I will not feel they've earned a tip. Servers should SERVE, and if they do not, it WILL BE reflected in the size of the tip I leave. If all they did was take my order & bring the check, I won't feel that they did their job in SERVING.
Bussers wear aprons, not always the cleanest, understandable, given the majority of their job description. Thanks, though, I'd rather not have them handling my food order in proximity to that apron--and how do I know they washed their hands after the last table they bussed?
Tipping aggravates me, as an outdated and 'expected' practice. The original meaning of "tip" in that sense was an acronym, meaning, "To Insure Promptness." It was given prior to service, not after, and was not dependent upon the amount of the tab. It was rather more like slipping the Maitre d' a bill of some significant denomination to assure seating at a preferred table.
The fact that the servers have to split their tips with bartenders and bussers is just wrong (and is not the customer's fault). Pay the people a living wage, adjust prices accordingly, and everyone will be happy. As it stands, the whole system is too complex, from customers having to figure the tip to servers having to figure out their splits, all the way up to filing their income tax reports.
You have to work hard at something to make it this complicated. Simplify and relax! ;-)