Competition is not the reason. The reason is workers choosing to improve things, invent things and make things more efficient. Competition is a way to incentivize people to do that, but it's not the only way.
Workers don't get to do that without some capital allocated. Rowing is one thing, deciding direction is just as important - and you'll find that the people deciding which way to row are largely trying to win.
The evidence for (price) competition improving production efficiency and product fit is overwhelming, examples abound in everyday life, it's hardly worth mentioning.
What are some notable examples "workers choosing to improve things"?