Karcher window cleaner - daft question

[FreshWest]

Is it just a really expensive squeegee or am I missing something?
Hate cleaning my windows as I never seem to get them streak free (and I've tried everything!) so thought as an investment I'd try one of these.

But I was under the impression it cleaned somehow as well? So do you clean the windows then use this after?
Sorry if this sounds dense but I'm struggling to see the benefit if that's all they do?

It's like a mini Hoover that sucks the water into a tank, leaving windows, tiles, shower screens dry.

You clean as normal and then run the 'squeegee' part down and it leaves it streak free.

I use it everyday to dry my tiles and shower screen. Less elbow grease needed to clean as you don't need to buff dry.

Only downside is you sometimes can't get to the bottom of the window if you have a window ledge, but all I do is run the window vac across the bottom of the window.

Even my husband (the cynic) thinks it's a worthwhile machine!