multiple reasons. 1. your age bracket is in the 30s while girls get the most messages in their early to mid 20s
2. you probably have boring pics
3. you're Asian and look Asian. nothings wrong with that but when it comes to dating some people are kinda racist and will overlook other races unless you are particularly hot or dont look the race you are.
4. depends on where you live. if you live somewhere like new york your inbox will always be jumping but somewhere less popular after a while it won't so much.
5. depends on what you said in your profile. many guys are on dating sites looking for a lay if you make it clear you dont want that you drive most of those types away reducing your message count.
in the end i think you shouldn't focus on how many messages you get just focus on finding a suitable partner.
Just because your profile is well written doesn't mean every man is going to message you. Mine is well written, too, but it talks a lot about watching my diet and working out. A guy who values Netflix, pizza, and soda isn't going to message me because I'm not like that.
People have to find you attractive AND interesting, not just one or the other. What you're looking for in terms of age, height, and ethnicity could be a factor, too, and distance.