This is an interesting question. I haven't played vanilla since the beta, but now I'm actually introducing a friend to Minecraft, and I decided to take him through vanilla first (I told him about mods of course, so I didn't just decide for him). It's interesting watching / helping him try to figure out and get used to some of the mechanics, and it reminds me of when I first played minecraft and all the things I had to figure out / get used to.
I feel like adding mods would make it too complicated. Imagine you're first time trying to make a rail system. Now think about doing it in Railcraft instead. Add the additional processing steps other mods have (like using Thermal expansion / IC2 to process iron), and it starts to get rather complex. Of course after you're used to Minecraft this added complexity gives you more capabilities and ultimately makes the game more fun, but in your first world of play it could certainly become frustrating. Add on top of that how hard it would be to look up items (NEI gives you crafting recipes, but for most mods it's not enough info about how things work or what they do). With vanilla you can go to many different sites and get a centralized database of what everything is, how to craft it, and how to use it. With modded (esp a mod pack) you need to know which mod an item comes from, find a site with info for the version of the mod you're using, and possibly watch a video or two about how that mod works before you can get into its mechanics. One may argue that "you can just use the vanilla items at first" but that defeats the point. It doesn't feel like it to those of us already used to it, but minecraft has a big learning curve.
I'm not saying you couldn't figure out modded minecraft initially like (presumably) direwolf did, just that it would take a much bigger investment of time, energy, and patience. I've been playing modded minecraft for a long time, and there's still a lot of things I haven't done in a lot of mods, even those that I've had for a long time.
I feel like adding mods would make it too complicated. Imagine you're first time trying to make a rail system. Now think about doing it in Railcraft instead. Add the additional processing steps other mods have (like using Thermal expansion / IC2 to process iron), and it starts to get rather complex. Of course after you're used to Minecraft this added complexity gives you more capabilities and ultimately makes the game more fun, but in your first world of play it could certainly become frustrating. Add on top of that how hard it would be to look up items (NEI gives you crafting recipes, but for most mods it's not enough info about how things work or what they do). With vanilla you can go to many different sites and get a centralized database of what everything is, how to craft it, and how to use it. With modded (esp a mod pack) you need to know which mod an item comes from, find a site with info for the version of the mod you're using, and possibly watch a video or two about how that mod works before you can get into its mechanics. One may argue that "you can just use the vanilla items at first" but that defeats the point. It doesn't feel like it to those of us already used to it, but minecraft has a big learning curve.
I'm not saying you couldn't figure out modded minecraft initially like (presumably) direwolf did, just that it would take a much bigger investment of time, energy, and patience. I've been playing modded minecraft for a long time, and there's still a lot of things I haven't done in a lot of mods, even those that I've had for a long time.
