That might be enough if the carpet starts relatively clean though - most of the deep down dirt gets pushed down through repeated use - stamping around a carpet

That might be enough if the carpet starts relatively clean though - most of the deep down dirt gets pushed down through repeated use - stamping around a carpet with muddy boots will definitely ruin things quick but if you're conscientious about usage you're usually leaving surface level dirt that a mini-vacuum can scoop up if it's run frequently enough. Roombas or similar things definitely can't keep a rug clean forever, but I think it's fair to say they'll make the times you need to get the heavy duty pet vac out less frequent.