I've dealt with retailers who had to remove clothing products for legal reasons, usually copyright complaints. It could be a knockoff of another design, or copyrighted characters on the clothes. If there is any backdoor way to get to the product page, they could be in trouble.
Designers often pull stuff from stores or negotiate exlusives with another store. This could have been some attempts of making sure some search results don't show up anymore.
They might have signed an agreement restricting "lowest advertised price". They're pretty common.
I can't think of a single reason. Some of the URLs still work too.
The point of robots.txt "Disallow"s is to tell search engine crawlers not to crawl a URL (which could exist). It's not to tell search engines that URLs matching a pattern don't exist.