Again, keep in mind my numbers are assuming a large, perfectly efficient solar panel under ideal conditions. Realistic numbers will be much worse. For example, most commercially available solar panels are 20-25% efficient.
5m^2 is too big for a car, and the panels are heavy and expensive. Toyota used to have a prius with a solar panel roof - it produced enough energy to run the fans (not the AC) while the car was parked on a hot day. Not even in the ballpark of the energy needed to move the car (and it was an expensive option).
That initial 1.3kW is ignoring atmospheric absorption. You lose some 300 W even at zenith without clouds. More if you're really far from the equator and/or it isn't currently solar noon. If you're in a city, you may be in shade a lot and certainly don't have the sun at its zenith for 4 hours regardless.
Affordable solar panels don't get 260W/m^2 peak. The solar panels on a car don't track the sun, so average power output is way below peak.
You don't get 1.3kW per square meter for 4 hours a day. 42,339 MW of PV installations produced 39,401 GWh of energy in 2017 in Germany[1], so on average you get peak power for just two hours a day with panels that are angled appropriately.
Then you get not all of you charge from the solar panel, but a quarter to a half. So what? That's still good. If the car basically had 20 free miles a day, that would mean much less reliance on plugging in.
