Obviously the extent of the tipping culture depends on where in the world you are... In the US, I would not fail to leave a tip to those who have served me. However, I would stop short of leaving a tip on the hotel bill.

One useful point about the Radisson LAX is that, if you have little luggage, you can walk from the terminals to the hotel, avoiding the bus transfers which can involve a long wait (and utter chaos) at peak times. You can follow the footpath that leaves the terminal area on the arrivals level, next to Terminal 1. There are a couple of roads to cross, and it's not a 'direct link' by a long chalk, but it saved me an awful lot of time when I was staying there.