Actually they do if they have to maintain it or want hire really good developers to maintain it. Not saying PHP doesn't meet those criteria, it might in a given region or situation, but just saying your dismissal of this consideration is way off base. Good luck hiring anyone passionate about good software development or recently graduating from decent CS department to work on your PHP apps. I'm sure you are a great developer with a real passion for your craft but you do realize that plus PHP makes you a very uncommon find, right?

If the client does not not care, why suffer by using something that is worse for you? I mean, you might as well use something that you like.

I don't get the logic here.

Another thing is that, if it it worse for you, it is automatically worse for the client. I am not sure why it is so hard to see. if your tool is bad, then your work ll suffer, and thus the client. So it is worse for them also..