A robust performance evaluation process does this just fine. If they do well they get a bonus, if they do poorly they get fired.
There is also no massive and obvious corruption risk in me paying either of those people to do a job as there is with a support engineer.
Maybe I should tip customs officers too, for processing my passport quickly and not looking too closely at my luggage?
Or perhaps if I take a speeding ticket to court, maybe I should tip the judge based on the outcome?
