I'm very much a capitalist who likes competition in industry. For the end consumer it provides a cheaper and more convenient in some cases as well. As far as undercut wages go, people don't have to work for them. Same as Deliveroo - a lot of people like the flexibility this sort of employment...
I see Southern Taxis have launched an app for customers to use as well, similar to Uber. Uber is huge success story and has promoted advancements in tech to local business as well. Can only be a good thing for the end consumer.