While I did fast travel everywhere, I did it because traveling wasn't as exciting as I thought it was. The environment is too static for tedious walking to be enjoyable. Most of the time, I get from point A to point B without seeing anything interesting happening on the road. The only interesting things I see are some random animals that charge at me, but that is it, really...
It doesn't take long to see everything that there is to see in the game.
Are you kidding me? I never fast travel and I always find interesting things to see. Besides the alchemy ingriedients I find along the way, there are the travelling bands of Khajiit that I can trade with or buy training in Speech or pick up an odd quest from, there are peddlers, there are random packs of bandits, Thalmor Justicators, farmers, Imperials, Stormcloaks, Giants, Dragons, etc. etc. Sure, some of the encounters seem a little stale after your third encounter with the same three Thalmor, for instance, but if you travel enough, you will see spawns of various things interacting with each other, and that is where the fun begins.
Last time I played I ran into a random Dragon who made the mistake of attacking a nearby giant. I watched and pot shotted the Dragon with a few arrows while the Dragon and giand battle it out. When it was over, I ran in to collect the soul and pick up the Dragon bones. Well, that overencumbered me, and I could not get away fast enough when the giant came after me. He came right up behind me and killed me with one swing of his big club.
I got really mad at that giant and when I reloaded, I started pot shotting the giant instead of the Dragon with arrows. The giant still won but he was a little weaker and I was not overencumbered when he came after me. It was a long battle and I had to reload a few times, but I finally slew that darn giant. In the process, however, the giant killed a poor farmer who wandered along and almost killed some Khajiit caravaners. After the battle, I trained Speechcraft from one of the Khajiit and it was enough to level up, so I picked stamina and had just enough increase in carry capacity to pick up all the dragon bones and the giant toe and still not be overencumbered (second spawn on that Dragon dropped fewer bones). Well, I hotfooted it back to Windhelm post haste.
These are the types of random encounters that you don't get if you fast travel everywhere. In all honesty, I much prefer these types of encounters to any of the scripted quests.