Because otherwise, if you divert the current H&C to Aldgate instead of
Aldgate East, you've got no trains running between Liverpool Street
and Aldgate East!

I think it would be much better idea to force people change at Tower
Hill (or build passenger walk tunnel between Aldgate and Aldgate East)
- current Aldgate junction is too crowded.

Yes, it's additional change for passengers, but it will result in
better service.