It's not the connection time, it's the risk of delays when travelling on two separate tickets and being denied boarding with no obligation on the airline to accommodate you.
You only have to be about 45 minutes late and the position is hopeless. With award bookings I know it's not easy, but I'd much, much prefer to be on a single ticket or at least a single alliance, at least to the extent that I couldn't afford to replace my trip without financial hardship.