Why so difficult to find a company to do construction work in Prague?

Recently I want to build a swimming pool in my yard.

It is easy to get an offer of the products from many companies, but none of them offers the preparation of installing (digging the hole on the ground and build the concrete platform for installing the tracks for coverage). They always say I need to contract another company to have these job done. Some of them did give me a contact from construction company,  but after I contacted those construction companies, none of them really show the interest in the project.

Usually those construction companies answer my first email in a day or two, and request some information like the location of my house, how big the pool will be etc, which I provided to them very quickly, and then they started to keep silence and seems losing the interest. They don't even bother to come and take a look, or give me an orientational offer. If I call them, they will apology and say they were quite busy and will give me an offer as soon as they could, but things won't change after I put down my phone. It seems that they don't want to work on this project, and they don't want to tell me the reason.

I recall that in November 2018, I tried to build an internal wall in the house with a new door installed. The situation was almost the same. Some companies even came and took a look, and then they just disappeared. When I called them, they said they are still evaluating the project etc. They didn't give me a quote of the price. Finally I had no choose but to have that job done by myself.

I really can't figure out why it is so difficult to find a company to do construction work in Prague. My house is not that far (in Nebušice) and it is not that difficult for them to come and work on it. They don't even ask for a price, so it is not because of money. Did I miss something that I should know? Any advice is appreciated.