As I listed elsewhere in the thread I've seen it several times, but I think Hollywood's use of laundromats (or apartment building communal laundry rooms) are used for 3 scenarios:

• The meet cute. It's a plausible place for people in different social circles to interact. The manic pixie dream girl and the uptight single lawyer both need to do laundry, so that's where they first meet. Easily contrived shenanigans with the props, underwear jokes etc. write themselves. It can also play with a dynamic that you don't often see in a dating environment: You meet someone in the bar or the club or at school or at work or whatever and you get to present the most polished version of yourself. Meet in the laundry room and now we get to see if you have some domestic skills which can indicate where in life the characters are.

• The domestic date. Characters that already know each other decide to visit the laundromat together because one or both has to do laundry and it's the only time they can have free. Thinking about the production side, I bet it's less of a pain in the ass to film than a dinner date, because you don't have to worry about continuity of the food etc. Easy reason for two people to be sitting in an environment together with nothing better to do than just talk, maybe you can busy their hands folding laundry or emptying/filling machines. Lots of opportunities for movie language, too. You can look down the rows of machines to frame the two in closer, you can look at them through the clear washer doors, either with it open or as if from inside one of the machines, etc.

• The excuse to be mutually half naked. At least two people and almost always mixed company are going to wash the clothes on their backs with nothing to change into, so they're going to sit around together in their underwear pretending very hard this is normal. This is mostly just a recipe for cheap cheesecake.

This is fun. Hey can we talk about some more weirdly common TV and movie scenes?

In Supernatural, Cass takes off his bloody clothes to wash them, but then he decides to use his remaining bucks on the vending machine instead, and he takes clean clothes from the lost and found.