The problem with eastern martial arts was that they focused too much on the ornamental and philosophical than pure utility. If you look at the history of MMA, in the beginning (early 90s) UFC was a free for all and practitioners of all arts were invited to fight. Eventually, the ornamental and philosophical arts were weeded out leaving only the effective arts left to compete.
The effective arts left standing to this day (for the most part):
- Brazilian jiu jitsu
- Judo
- Greco-Roman wrestling
- Boxing (Western)
- Muay Thai (boxing)
- Kickboxing
- Karate
The only one of those with a hint of "philosophy" you're thinking of would be Karate. Don't get me wrong, they all have philosophies, they're just not up-their-own-arse about it. It's balanced.
What was the question again? Why do Eastern arts involve more philosophy? I don't know, but they're not the ones left standing in the realm of effectiveness in real life scenarios. That doesn't mean I totally discount eastern philosophies. Some of my favorite books: Book of Five Rings, Tao of Jeet Kune Do, Hagakure. I think philosophy and science should be balanced in a warrior.