Surely that means they know how to act around others?
No, is the short answer to that.
The long version goes as follows: yes, they are polite, but politeness is a fundamental expectation, not a high bar, and not even a middling bar.
Your eldest is asking you very nicely to let him behave like a decent young man. You're ignoring him. You're not being kind here yourself, OP. You're modeling not listening to people when they tell you what they need. That is what your sons are seeing.
They're also seeing a woman whose entire identity seems to revolve around doing quite servile tasks for them. For starters, it's embarrassing for them. But more importantly, they're not seeing a woman whose life is full of her own projects that are not related to them.
Will they shy away from such a woman when they're looking for a life partner?
What comfort zone are you creating for them?
What gendered dynamic of family life are you presenting to them?
What bedrock unexamined assumptions are you instilling in them? What you say is not as important as what you do.
Above all, what approach to relationship are you presenting to them? There's more to relationships than filling physical needs.
What needs of your own are you filling here, to the detriment of your sons?
What effect does ignoring their emotional needs have on them?
Does it tie them to you in a debt of gratitude? Is that what you're looking for here?
Does it make them feel unable to be direct with you when expressing their needs? Are they looking after your feelings instead of getting up and bringing their own plates to the kitchen or sorting out their own laundry? If so, who is the parent here?
How would your sons feel if they had a mum who took up 5k running or joined an evening pottery class or a local choir and this meant they would have to cook, clean up, and do their own ironing two or three evenings a week? How comfortable would you feel putting your name down for activities and telling them your news?
You seem to associate serviliry with maintaining a relationship. Is there an idea in your head that keeping them fairly helpless in the domestic sphere will mean your hope that they would return home after a failed relationship will become a prophecy? I'm not saying you're planning for their relationships to end in painful circumstances, but you're not planning for things to work out swimmingly for them as equal partners in running a home either. Is there a teeny tiny little part of you that would feel a bit jealous of any women they chose as a girlfriend or partner? Would you feel rejected, deep down?
A very important consideration here that you may not have thought about is the effect of domestic incompetence on the self esteem of teens in every other area of their lives. Academics, career, willingness to apply for challenging roles, ability to negotiate a salary - ambition and drive in general can be scuttled by being treated as a helpless child long after teens cease to be children. Resilience is another important victim of mollycoddling. Your hope that they would return to you and not rely on their own gumption if they had a big setback is concerning.
Childhood neglect has huge ramifications here. Did you absorb a message that you weren't valued or valuable in your own right? That dreams or aspirations of yours weren't important? That physical care was the only important part of a parent-child relationship? Did you feel you had to work hard for love or attention?