The bellhop comes into contact with more people, and is tipped proportionally less on average. A bellhop spends 3-5 minutes on me, a server spends 15-20 minutes[1]. A bellhop gets a $0-2 tip, a server gets a $0-5 tip.

[1] A server who can handle three 4-tops who sit for two hours is only spending about 10 minutes on each customer, so my 15-20 is a very generous estimate.