Inability to maintain quality can also be a reason for a business to fail, Customer's always want the best, the moment their is lack of value it can change the mind of Customer's to go after something else and may not come back. Business can also fail when you don't know what your customer want.
Of course, if we can't maintain the product quality or the quality of our service, the customers may feel disappointed. The customers always want to get the best quality, they will always compare our quality with others. When they think others have better quality, they will never come back again and totally move to another one. That's why maintaining the quality has a big role to keep the trust among the customers.
Some customers even expect for an improve of our quality. They may feel bored if there is no improvement at all, they may judge we have no innovation. But this type of customers mostly come from the upper-middle class people. But if the most customers come from the low class people, they only focus on price. As long as it is cheap enough, they will never complain.