When they are starting out, they generate a buzz while providing superior food and service. The chain grows rapidly and is suddenly in every major market.
Once the chain matures and saturates the marketplace, it becomes difficult to maintain the bottom line. Cost cutting ensues. Portions are reduced. Many entrees are shipped frozen and microwaved on the premises. You have to start asking the waitstaff for extra napkins and for salt and pepper shakers to be brought to the table. Shortcuts are taken on ingredients. The drinks are a tad watered down. Applebees is a perfect example of this.
Eventually the chain starts closing restaurants and endures a slow (and sometimes rapid) death.
Only a few manage to break the cycle. Texas Roadhouse is an example.