Does anyone else think that the death system in harry potter is very undernoted?

i mean when someone dies they can go into a portrait and then communicate with the living, so why couldn't harry's parents have had portraits and he could have talked to them all the time? and what about dumbledore was harry able to spend days on end talking to him in the headmaster's ofice? and sirius surely he must have had a portrait in grimauld place harry would have loved to talk to him, am i missing something ive read through the books before it was a while ago right enough..