I personally find riding to take more effort than walking. Maybe if you lived somewhere flat, with lower temperates and low humidity, but here in Iowa we have hills to climb, and the heat and humidity to deal with.

When I walk to work, I have a bead of sweat on my forehead/brow from the sun beating on me. When I ride to work, I have a nice ring of sweat worked up around my neck, under arms, etc. And it's only a 2.5 mile ride!

I suppose my weight also factors in to it a bit.

However, I have come to some of the same observations - but a different conclusion. Biking vs driving is basically a wash due to all the stop signs, traffic, etc on my route, and the difference in having to go out to my car, start it up, park in the back of the (full) parking lot at work, walk into the building, etc vs having the bike rack right next to the door and being out of the parking lot long before anybody else has even gotten in their cars.

For me, it's not lazy - it's practical. I would imagine it would be a no-brainier in more metro areas with heavier traffic.