"Aisle 2C: may be not so. If you buy a seat for a musical instrument you do not get the baggage allowance for that seat. IMHO that is bordering on ethical/moral breach of contract. The seat price includes all the goodies. What you choose to do with that seat is up to you, if legal. It would be an interesting test case if any one chose to test it. Mind you, same goes for no pooling of baggage within a group for whom one person paid all the tickets. That would also make an interesting test case. "
Rat 5, if there was one airline company on this earth who would probably try to have it both ways, you just know it would be Ryanair ! As it happens, my little fella is 2 now, so he has to pay (or rather I have to !) like everyone else for a seat. The seat would be in the baby's name though, which might make a difference. It is just the parents choose not to tell them his age. If they tried to deny baggage allowance, I'd reckon the parents would have to win in the small claims court.
Thinking about it, I think it sad one has to think of an airline company in those terms (or any company).