Also, people can't do it themselves because they don't know how to and most don't even know about Wordpress.
But they can find out, can't they, and learn? This time last year I knew nothing of building web sites and had never heard of Wordpress. I started my company in January, needed a website, but with hardly any money set about sorting it out myself.
I realise that my site still needs a lot of work, but I have the basics there, and for the first few months it has served its purpose. If I had more time, then I could learn more about Wordpress, but too busy working for my company, earning money.To improve it to what I want I realise that I am going to have to pay another person/company, in the next few months, to create the site that I want.
From what little I have learnt, I would not only be looking for someone who could improve (which won't be difficult) my website, but to also add any little "tweaks" that I may want. And although I have a good idea now exactly of what I want, I wouldn't be surprised if, when I see it, I would still want changes. Being offered a web site as quickly as you are offering them would not be practical for me - where is the time to think and decide what is really needed/wanted. Bearing in mind that I still have to run my company, I couldn't promise that I could come back to you with everything you need as quick as you require it.
It seems like you will expect all your clients to conform to your restrictions, but I can't see that happening. You do need to be flexible - which you probably need to be in most businesses.
I do wish you well in your new business, and certainly hope that you succeed. As a small business, which has nothing to do with designing websites, just thought I would give a view point from a potential clients point of view.