I think that's partially due to the fact that syndication, national providers selling programs to local affiliates is a larger thing here in the States. Those programs go out at a specific time and often the local stations are just relays and can't time shift things.
Contrasted against the system in the UK with the BBC where there's not really a local affiliate but a national station. In that case it seems much easier to shift for longer running programs.
Both the BBC and ITV are regional, with a core national schedule but lots of opt-outs. Most news broadcasts will be followed by a regional news programme. BBC Scotland, Wales and Northern Ireland regularly opt-out of the main schedule to show locally-produced programmes.
Contrasted against the system in the UK with the BBC where there's not really a local affiliate but a national station. In that case it seems much easier to shift for longer running programs.