I commute by bike so have a few just for that depending on the weather (ice/snow or not) and where I will be travelling to e.g will my Brompton suit better or not? Its my primary mode of transport so prefer to have options open to me.
I also have a TT bike and a couple of fair (one pretty much guaranteed dry) weather road bikes.
When buying my current home space for said bikes, and the 5 Mrs Syd has, was an important factor.
If I didn’t have the space, and didn’t commute by bike, one would likely suffice though two, one all weather and one fair weather, would be better.
Its been known for me to do a 50 mile ‘commute’ to or from work on nice summer days (the normal commute at that time was 6 miles).