The main problem at St Albans is that passengers from that city do not want to spend more than about 20 minutes on their morning train into London. This is why they jam themselves uncomfortably into the fast trains and ignore the stopping service that conveniently starts at St Albans, on which they'd all definitely get a seat. I know the "stopper" takes a bit longer, but as it calls at West Hampstead it would allow a convenient interchange with the Jubilee line for passengers wanting Canary Wharf.
Those of us who actually commute from St Albans will tell you that the peak semi fast trains (taking 8 minutes longer than a fast, none of which start from St Albans) each have around 2-300 or so people joining at St Albans, and the stoppers (+16 minutes) about 100, ie trading time for a seat. Anyone who commutes to Canary Wharf already gets them for the change at W Hampstead to the Jubilee (About 3-400 people alight each peak semi fast there, the staff at the W Hamp LU station can set their watches by it).
