I, for instance, got an IO option on my first mortgage when I bought my house in 2003. My second was always fully amortized. Both are 30 year fixed loans.
I elected to pay IO for the first few years I was in the house on the first mortgage. Then I called the bank and increased my mortgage payment to start paying principle.
It gave me some breathing room while I adjusted to a much higher payment than I was paying in rent. I could have afforded the whole nut but I knew my salary would be rising so took advantage of the lower payment for a short time.
There is nothing wrong with these loans if used correctly. I haven’t pulled a penny out of my house and I have zero consumer debt other than a car payment.