In my case, once I want to be close with you, I want to be CLOSE with you, if you catch my drift.
Re: gifts, service, words -
Gifts - much like already mentioned - it's usually crap I don't need, and don't have space for, or if I do want it, it's not the exact kind I want. I like giving gifts, and am good at it, but don't really need anything in return. I also hate thank you notes. Finally, there's always the ridiculous social dance that goes along with it. You never can express how you actually feel when receiving a gift. May be mistaken for bribery.
Service - I don't want your service; I want your help. That turns it from service into quality time. Likewise, if you do something for me, it seems very neutral, because it's expected that I'll hit you back up in the future. It's maintaining the relationship, instead of building it. Can be mistaken for currying favors.
Words - I don't like words of affirmation, because it once again starts up the silly social dance of acting humble even when you're feeling confident or even proud of yourself. It's annoyingly inauthentic (now you're going to think I'm an NF, lol), and can often be mistaken for flattery.