Street photography is often said to be the most accessible, egalitarian form of photography. You don't need an expensive camera or a particular lens, you don't need an amazing landscape or an accomplished model, and you probably don't need to travel far. You do typically need some people around and perhaps a lot of patience, but there are possibilities for most of us in a nearby city, town, village or beach. (And yes, I know I'm particularly fortunate to have Jersey City and New York so easily accessible).
Just in terms of practice, street photography probably gives you the chance to photograph more regularly than you might otherwise. But there are also specific skills in street photography that translate very well to other genres.
Much street photography is about candid moments. Interactions between people, or compositions that exist only for a fraction of a second. It takes observation skills, technical ability, speed and compositional awareness to capture those moments effectively and artistically, and to convey a message to a viewer. Not only are these important skills for documentary photography, but also for documentary styles in event photography and wedding photography. Being able to capture a genuine candid moment at a wedding, as Kevin Mullins does so effectively for example, takes many of the skills of a good street photographer. Plus probably a good suit.
Street portraits are another good example. When you introduce yourself to a stranger to take their portrait, you probably won't have a lot of time with them. Maybe a few minutes, maybe only long enough for two or three shots. If you can create a strong portrait in that time with someone you don't know, you're well equipped for a longer portrait session, or perhaps a photoshoot with a client where similar time pressures apply.
You will also learn about light. How to see it, find it and use it as a part of your compositions. There isn't much that is more fundamental to photography than that.
(If you're interested in learning more, my 2017 street photography workshops in New York are now open for bookings.)