If I'm there doing an irrigation service I will leave them a quote for fertilizer. If the customer says they are happy with who they have I leave it at that. Now if they say they are happy and I am positive I can provide better service (theres obvious fert burns/striping/insect damage/weed issues) or theres a tg/cl sign then I will explain how I can provide a better service. If the lawn looks great and they say they are happy then I leave it at that, and I hope that if the customer decides to switch services they remember me. I'm not going to lowball to steal a job away from a guy doing quality work because next week he might be on one of my lawns and I don't want to give him a reason to try to steal a job from me.
Why do people not respect us as they do other tradesmen? Because every Tom, Dick, and Harry doesn't think he can be a plumber or electrician!