Jeremy isn't exactly the worlds greatest actor, hasn't really done anything /that/ critically notable… and is now firmly washed up.
He's not had a decent acting gig for a long time, so has done low-rent stuff to stay relevant. That pays his (apparently lavish lifestyle, hobnobbing at garden parties with Christophe DuChump) but in turn, it makes him a less attractive casting for proper TV work.
People flicking through the
Radio Times see a listing for a new drama starring someone they saw most recently on
Celeb Colonoscopy Island* type shows will likely think:
'if that's the calibre of star involved… I'll Roofix my own face instead of watching' - that puts casting agents off.
The fact he's now sunken to doing shopping TV compounds that - suggests even the low-rent TV shows don't want him!
Shopping TV is basically a life-support machine for former celebs. They put their careers into a self-induced coma hoping things will recover, but few ever wake out of. Fact is, they'll need that machine more than it will need them.
And eventually it'll be turned off
*Yes I made that up, but chances are a Channel 5 TV exec considered it at some point …