Developers don't "target" character buildings as part of some nefarious scheme. They look for value propositions, opportunities for consolidation (ever try building a parkade on a single lot?) and sites in good locations. I suspect part of the reason why lots like KFC, Wendy's, or MacDonalds are not "targeted" is because you have to work through their real estate divisions, which sounds like months, if not years, of headaches just to get a response.
High streets evolve. Find me any high street in a really urban city (European high streets for example), that are nothing but independent shops. Go to Kalvertstraat in Amsterdam or Gracia in Barcelona, and you will be hard pressed to find a mom & pop shop, and you couldn't throw a stone without hitting a Zara or H&M. Boutique retail is awesome, but it eventually gets priced out, but it just moves a few blocks away. There is nothing wrong with that.