Putting plastic in a landfill sequesters carbon, has less emissions in transportation, and doesn’t require paying people to sort it (ultimately born by us chumps paying extra to recycle it - if recycling were truly worth it, they’d be paying us to take it away, or at least discount our garbage service for separating out plastics). Landfills already have mitigations in place for groundwater contamination since landfills can have much more harmful things than micro plastics seep out of them.
Not to mention all the micro labor involved in cleaning plastic, and in sorting it for people who aren’t lucky enough to have single stream recycling. Maybe it makes some people feel good but it seems like a distraction and waste of time just to make an unviable activity slightly more viable (if plastic recycling were actually viable this would be centralized since it’s more efficient).
I completely support recycling for materials like aluminum and glass that make sense to recycle, but recycling plastic has never made sense economically, and putting it in a landfill isn’t that bad.