To except the host to introduce you to the other people there?

[MrCollinsandhisboiledpotatoes]

Today a friend invited me to lunch in a pub garden, we took our kids along as there's a play area in the garden. She mentioned her sister and another friend would be there also with their kids.
Arrived last and friend was there. I said hello to friend and hugged, nodded hello to the other people and sat down.... expected friend to then say "this is so and so and this is so and so, everyone, this is Mr Collins, nice to meet you, nice to meet you too, etc" but she said nothing?
This isn't the first time this has happened either as twice in the last few months I've been to friends houses for small evening gatherings and haven't been introduced to the people I don't know or asked "you know so and so, don't you?"
Are people just not doing this any more? I thought it was good manners and I've always done it as second nature, never even thought about it?

It's so awkward to introduce yourself. To me, anyway!

As in crystal balls....physic..... its an in joke I guess.

I think if she invited you it would have been polite on her part to offer a brief introduction to the other people there.

I personally would introduce people in this scenario but I think people are perfectly capable of doing it themselves. You’re being a bit precious.

Everybody’s capable of doing it themselves, it doesn’t make it any less rude or odd not to.

Oh! Sorry, that didn't click at all!

Like most, I generally think I would introduce people (if I remembered they didn't know each other), but then, I am very happy to say "I am Just...don't think we've met" and hold out a hand to shake.
I've not noticed it as being a 'thing' in terms of it declining. I find more often people introduce people who then say "Yes, we met last year" or something.

I just introduce myself. I don’t need someone to do it for me.