First I couldn't afford motorcycle boots, therefore I used my German military boots. Later I could afford real motorcycle boots, but I was so happy with my military boots that I didn't want any, and I'm still at this point. They are not waterproof, they are leather, but I can live with it, even expensive Goretex boots are not 100% waterproof in the long run.
Since I do a lot of sight seeing on my motorcycle trips I need boots that I can walk in for several hours.
Motocross boots are to stiff to walk in, and boots for crotch rockets have very thin soles and therefore are out too. Boots, like I want them are rare, and since I'm happy with my military boots I'll stick with them for now.