Lots of reasons. Democratic socialism doesn't eliminate private ownership the way communism does, people can still get rich, own companies, and buy jet skis, but they can't take a successful company that hundreds of people have helped build and centred their lives around and hand control of it to their unqualified, arrogant, spoiled children to run into the ground, among other things. Here's a decent basic summary:
*Democratic socialism combines political democracy with public, cooperative or state ownership of key industries while maintaining elections, civil liberties and pluralism. It seeks to reduce inequality and ensure that wealth and power serve the public good through taxation, regulation and social programs.
Communism, rooted in Marxist theory, envisions a classless, stateless society where all property is collectively owned. In practice, communist states have often used centralized, one-party government control to pursue those aims.* (edit: don't know why italics isn't working)