It can sometimes quicker staying on the bus than changing to light rail.
Example Gateshead Interchange to Eldon Square is timed to take 10 minutes on the bus, Metro is timed at 5 minutes Gateshead-Haymarket which is nearest station to Eldon Square, but the added situation of changing from bus, getting down to the Metro platform, waiting for the Metro, getting off at the other end, then going up to the street, when you'd already be there if you stayed on the bus, more so if you just missed the Metro.