Well it is just as prepositions in English.
Nope. It is quite logical dative. If you help me then you give me help. You generally do not act directly on me, but on some other object for my sake.Take this example: the verb "помочь/помогать" (to help). It obviously requires direct object: when you help someone, you're doing the act of helping directly to him/her. So you would expect it to take the accusative case. Well, it doesn't. It takes the dative: помочь кому-нибудь.
Grammar is the way of thinking.