Two different promises
A conventional loan with less than twenty per cent down carries private mortgage insurance, and that insurance is cancellable. Once the loan reaches the threshold the lender is obliged to drop it, and you can ask earlier if the property has appreciated. It is a temporary cost with a defined end.
FHA is a different arrangement. Under ten per cent down, its mortgage insurance premium lasts the life of the loan. It does not fall away when you reach an equity level, because it is not priced on your equity. It is what makes the wider credit box possible in the first place.