You should also remember that there is a standard handover/assume procedure between all sectors.
Not all sectors, even if you are high level in IFR. In many parts of the world, you are expected to free call. I remember once hearing ATC getting hot tempered with a speedbird because they hadn't free called in advance, had no clearance to enter the FIR, and were very close to being intercepted.
Even if it's the next controller in the same FIR, you can sometimes expect to have to pass your full flight details.
In one region there is airspace covering about 60nm where you aren't within VHF range of any controller at all, with an FIR boundary in the middle of it. I once asked if my details can be passed on. The chap said that his phone hasn't worked for years. He didn't have a correct onward frequency, and the charted frequencies were useless. Guard was often used as the first contact with the next controller.
Then there's Northern Cyprus. There's no chance of an appropriate hand over. Guard is often used by "both sides" to get in touch with flights who aren't juggling the frequencies correctly / didn't do their homework.