Why? Some people have more than 1 weak ankle, or have more than 1 injury. What an ignorant comment to make.
Anyway, it depends on what you mean by ankle supports? There's a few available. My ankles are weak, have been since I was a kid, the result of mutiple major sprains. So I tend to wear wraps:
http://www.support4physio.co.uk/lp-ankle-wrap.php
Covered by the normal neoprene supports:
http://cranesproduction.net/index.php?main_page=product_info&products_id=71
Then, if I still get an injury (last one I didn't reset the kick fast enough while my sparring partner returned low, hit me just above the ankle while on one foot) I have one of these:
http://reviews.protherapysupplies.c.../18759-Mueller-Hg80-Ankle-Brace-w-Straps.html
Helps prevent injuries inasmuch as you can when training/sparring, also helps me get back on my feet and into training quicker when I do get injured.