likely used by vendor as sales strategy to upgrade device:

we will give you patch for this EOL 0day, but this will be the last one. Please buy new version and btw here is 20% discount code, you are welcome

Still better than leaving devices unpatched. The end user still has the final word, can totally refuse to buy a new one if he/she doesn't think getting a new one is worth it.

they could offer to send you a $15 grubhub gift card for your trouble