Paul Corfield wrote:

It's not possible for us to know the driver's motives. I have had half
empty double deck buses drive past stops with people waiting at them
and I have seen drivers fail to appreciate that while the lower deck
may be rammed the upper deck has seats. It's no fun when you're the
poor soul trying to get on the bus and you can see there is space.
Your driver might just have been having a bad day - who knows?

He seemed in a reasonably good mood when one passenger was asking which bus
to change to for Bethnal Green (it sounded like once again insufficient
information about alternate bus routes was provided for the Central Line).
But even if it's just the driver having a bad day, it's a awfully common
experience on the 25 and from what I've seen, both from on the bus and from
the pavement when it's stuck at lights, the bus usually looks pretty crowded
on such low numbers. And passengers are definitely moving down the aisles
and using what space they can.