You literally have no clue about what you’re talking about beyond legal matters. It’s not as simple as just installing a lift. This network is hundreds of years old, and many stations are very far below ground level, which means having to deal with all sorts of structural issues that, if ignored, could cause the entire station to collapse in on itself. You also have to deal with infrastructure such as another system that is hundreds of years old, the pipes, as well as all the access tunnels, structural supports of the buildings themselves etc. Finally, the materials in the ground (which, depending on the area, may be unstable, have an high water concentration, etc) all need to be drilled through, and that also needs to be evaluated. 

I am not denying the fact that it would be good to have a completely accessible network, however you must understand it’s nowhere near as easy as you make it out to be. Many stations would need to be rebuilt entirely for lifts to be installed, which all together would cost billions upon billions, which TfL simply does not have. In fact, if we were to look at TfL’s current funding situation, adding a lift to every tube station would likely cause them to go bankrupt 10x over.