The windscreen wiper is very likely to be outsourced to a 3rd party company, and they can reduce costs by having a repeatable design. In terms of a blade going on a straight line, it’s much easier to rotate a wiper blade from a motor than translate that into a linear movement.
It’s worth nothing that other systems exist (https://www.a1-windscreens.co.uk/news/windscreen-wiper-movem...), but much less common.
Here's a Hyundai engineer talking about wipers: https://www.digitalengineering247.com/article/the-back-and-f...
1) having a single attaching point for the wipers makes designing stuff around it more simple
2) accurate curved tracks that match windscreens are hard to manufacture, secure and keep in shape
3) Keeping constant force for all parts of the windscreen is much harder with a track (high and low spots, change the window screen, the track needs adjusting too)
4) standard bearings are much more simple to seal
5) linear bearing as a pain to seal
6) tracks are much harder to seal against the weather
7) tracks need more lubrication
Some vehicles have pantograph wipers which work horizontally, however that's a more complex design than the usual simple pivot, and you can't "park" the wipers out of view when they're not in use so they're more obstructive. They're sometimes used on car rear windows but mostly seen on commercial vehicle windshields.
Some cars (mostly benzes) also have eccentric arc systems where the wiper arm extends and retracts to cover more windshield with a single pivot.