Touristy thermal pool lagoon vs community swimming pool

Don't be fooled, locals go to both as do visitors. Locals do the local pools daily though, which of course they don't do the more expensive lagoons daily.

We have done both and they are both great. Not all of the lagoons are expensive. Secret Lagoon is not, and is about $35 pp. The local pools are about $10.

The locals pools are not just used for exercise, and in fact most of the time the locals are just soaking in the hot tubs and doing cold plunges and the saunas.

Do not that at any of these places, the biggest thing to remember is that you must shower completely naked, and THEN get into your swimsuit. They do not use chlorine or any chemicals, so you need to be as clean as possible for yourself and everyone else. The local pools are almost always open showers, like what middle school used to be;) The commercial lagoons almost always have private stalls, but some do not, such as Secret Lagoon.

Most of the time we do a mix of local pools and the lagoons. The are all unique in their own way, so we try to hit as many as we can on each of our trips. You can't go wrong with either.

At the risk of sounding disrespectful, I am still not understanding the attraction of an Icelandic local pool. I get why people want to go to Blue Lagoon or whatever, because it is a tourist attraction and the operator makes it a unique experience - whether it's the milky white water, or the 7 step ritual, or the view of the nature.... But a local pool has none of that. All you are experiencing is sterile mosaic walls and noisy sounds from other swimmers, right? If I take a trip to Grand Canyon or Yellowstone (the closest analogy of US locations I can think of to Iceland), it will never occur to me to find a local gym and spend half a day in a pool or a hot tub with a bunch of locals.

What am I missing?

Several years ago I visited a local pool in Reykjavik while on a long layover on my way to Europe. On the return trip I went to the Blue Lagoon on my shorter, but still lengthy layover. The local pool I went to (forget the name) was much like any outdoor pool here at home. I was there during a time when some lap lanes were open as well as a more "open swim" (play time). I went to the pool because I had about 13hrs to kill and being a swimmer liked the idea of stretching out and swimming after several hours on a plane and a few more ahead of me. I was already going to be in the downtown area to visit museums during that time so it was just easier to head straight to town on that layover. On my way back my layover was shorter and so I only booked the Blue Lagoon.

If you want to actually swim a few laps and get some excercise in, find a local pool. If your want to just soak and be in warm water, possibly with a drink in your hand, head to the Blue Lagoon or similar. For what it's worth both experiences were exactly what I was looking for in that moment.

OP, you actually answered your own question in your original post. It is about experiencing
life as the locals do. You may walk away from scratching your head, or befuddled, but, you'll
have a different experience than if you went to a tourist-oriented place.

From reading your post, I think some of this has to do with your own mindset. Would you go
to a local restaurant in Paris to see what the locals eat as opposed to Jules Verne at the Eiffel
Tower... You know what your local experience is, and you're used to it. Someone from
another country may want to go there since they have no idea what it's like and they are
curious. Not saying they will rave about it afterwards, but if you're not curious, what are
you travelling for?

Phaser--The locals pools do have their own great attributes. One in downtown Reykjavik has rooftop hot tubs and we have enjoyed that one a number of times. They have kiddie areas that are only a foot or so deep. Some have waterslides. The saunas and cold plunges are routinely used with the locals, as are the hot tubs. Like anything, some offer more than others, but FWIW we have never had a bad or even just meh experience at them. Sometimes you talk with locals and sometimes with other travelers. Either way, we enjoy it.