The cache is to minimize the bandwidth consumption of the Skype for Business (Lync) client, since it retrieves a lot of information from cache. This caching information is used when the client does e.g. The desktop client of Skype for Business (or Lync 2010 / Lync 2013) cache a lot of information on the PC.
I recently had a scenario, where clearing up the current Skype for Business Profile solved our problem, I our case the Skype for Business client had problems logging on and it was not related to network or DNS.
