Yep, thats true. But you have to think about it. Most people don't buy MP3 players because of their features. They buy them if they know they will work properly and they look good. Thats why everybody buys iPod's. iPod's will never support .wma's or .wmv's but they may support new video types later on. Still if you want a bunch of features that you'll never use, look beyond the iPod.
In terms of music iPods don't need to support Windows media formats. They use iTunes to sync music to the device from the library and you can easily convert the WMAs to better more compatible formats anyway. In terms of video, they do need to add support for more codecs.