I've just been doing it so long and so regularly that it's become my comfort zone.
We all work within our own comfort zones. I feel trapped and claustrophobic inside a motor vehicle these days, even one as large as a city bus, which I had to use for two days earlier this month due to a mechanical. I couldn't wait to get back outside. It's the same with cars. I feel completely uncomfortable inside them--even if I'm the one who's driving. Given that once upon a time I drove sports sedans and Car & Driver was my favorite magazine, it's been quite a transformation.
For those who wonder how I've chosen to manage the issues that No Motor raised, first are the studded snow tires. I've never fallen in the winter. Well, except that one time when I took the studs off a day or two too early...
I too keep my bikes inside both at home and at work. Flooring choices help a lot. Lino at work, hardwoods at home. (And a landlord who, when I asked if he had any objections to my pushing a slushy bike through the hallways replied, "It doesn't track in more than people's boots, right?")
I have a trainer mat just inside the door where I take off my boots. It also catches drips from the bike while it stands there waiting for me. After a quick rinse, it's hung over a boot tray to catch the drips. No rinsing facilities at work, so the bike just hangs and drips into a boot tray. At break time I tilt it a bit to drain what's collected in the fender.