Got one a few years ago. (They appear to be covering the country slowly.) I thought it was incredibly intrusive so I never returned it. Nothing happened.
There's no intent to cover all residences in the country, it's a random monthly sampling of addresses.
The reason for it is that things change year to year, and only having data every 10 years means data is pretty old by the time 9 years have passed.
The questions about time leaving for work, commute time, etc. are for road construction planning.
My elderly mother “helpfully” filled out the d____d thing and sent it in for us !
All it takes is one person in the family to “cooperate” and all your privacy and also any firearms ,etc. etc. are at risk.
The government type know a woman in the house is much less likely to defy them.