The alternative to competition is monopoly, where there s a single supplier of a good or a service and that person konwing there s no competition has the opportunity to put up prices. There s no great pressure on them to keep their costs down and to be efficient.
So it s that competitive pressure that tends to make markets respond to what consumers want, to offer the best deals, and also to be technically progressive, to innovate under the pressure of competition.
You may get consumers who want very high quality services satisfied, but at a higher price. And the people who want no-frills service and cheap product will also get it at the other end of the market. So competition allows a range of variety to occur in a market.
The benefit to society of competition is that it makes a major contribution to the fundamental economic issue, which is the scarcity of productive resources. It means that on the production side, there is maximum pressure to conserve the use of those scarce productive resources.
On the demand side it also rations consumer demand appropriately, and it also tends to mean that the variety of consumer needs can be met.