Because the city has a lot of military in it. It's how Ukraine has mostly fought. Because it is quite urbanised. It cannot beat the Russian Army on the field. So instead it digs into a city. A city it can hide in among civilians. Civilians Men and Women it conscripts. A city of that size also has military installations. Ukraine did or does have a militarised line outside the Donbass and Luhansk regions with trenches and bunkers, because of a decade of fighting. But the rest of Ukraine largely hasn't. Any military installions have largely been hit. Airfields, Navy, and standing bases. There are even reports that they stockpiled munitions at the nuclear reactors.

But the Ukrainians are using their cities. Like the Syrians have. Even like the Taliban.

In regards to his phone whatever largely in a green zone. It presumably isn't that intention, although previous it uses everything when repelling.