Yes, there are many reasons to own a patents portfolio other than blocking competitors.

Having a big patent portfolio position a company like an innovator, for seeking investors but also for the customers, its a marketing strategy too.

It also help in using existing patents from other companies by making cross-licenses agreements, explicitly or not, a kind of cold war: if you sue me I will sue you! Its he reason why Google bought Motorola smartphone division to take the patent portfolio of Motorola in mobile phone technologies.