This is because partners have to prove their competency in delivering repairs on behalf of the brand, and certain lofty standards will need to be upheld. With that said, one complaint from many people is that partners of these brand names may charge a premium price when using their services.
This leads to the next point, and this is that using an affiliated partner offering Apple, Dell or Toshiba laptop repairs or PC repairs will often mean that your warranty is kept fully intact, which is not the case when you do not use an official brand partner. If you are looking for Toshiba laptop repairs for example, choosing a Toshiba affiliated provider of repairs services is likely to get you the level of professionalism that you want and need.