Simply to increase their supply of new products. Companies need new products to survive. As old products become obsolete, new products must come on stream to replace the lost revenue. Companies need new products to grow. Every company wants to increase its market share, which requires a continuing stream of new and improved products.
All companies engage in in-house product development.
The smarter companies also look outside to augment their resources and give them a competitive edge over those who don't. Why companies resist dealing with outside inventors. Of a 1001 reasons, the first 999 are fear of lawsuits. Companies have much more to fear from outside inventors than inventors have to fear from companies. When a company deals with outside inventors, it exposes itself to frivolous lawsuits.