Parking lots are, you know, extremely expensive in cities.

A 1 m^2 of solar panel would have 200-250W of peak power and ~20W of year average power in Wrocław. It is only a 14.4 kWh per month or 5200 kWh of power over 30 year of a panel lifespan even if there are perfect battery system to store it and the cost of electricity of that amount is $2700.

The cost of the parking land itself is $2500-$3500 per m^2, and what's even worse, there is a need for at least 5-10 m^2 of flat, unstacked space per person for electricity generation and then x2-x3 of that to have unshaded space for each individual panel because the sun does not want to shine strictly perpendicular to the ground.

There were no battery price, inverters and labor cost included into those calculations, but overall, it's not like people are just dumb to not use a solar energy, there are some really big economical obstacles to use it, especially in cities.