Call me old fashioned but I really, really, hate the prevailing entitled attitude that some pps have mentioned here, that just because someone wants to do something pleasant for someone else, eg they obviously wanted to host, so the thanking aspect isn’t important.
You could extrapolate that to any scenario where a person does something nice for someone else eg Aunt Maude really wanted to buy my dc a present so doesn’t require a thank you.
It is possible as a host to thoroughly enjoy people’s company and the overall experience of planning and cooking and serving but still find the other aspects like food shopping and washing up a bit tedious.
I think people who don’t host, don’t fully realise what goes in to it. Or people haven’t thought about what it involves. I don’t think it’s a coincidence that I often receive the most thoughtful thank you messages from those who cook and entertain themselves.
Plus ingredients are expensive nowadays. We have stopped entertaining as much, because the price of everything has really shot up and it’s just not possible for anything but a very special occasion.
So yes if someone among our friendship group goes to the time, trouble and the cost of entertaining at home, then we will thank them verbally afterwards and follow up with a text or email the next day because we are truly grateful. And as that Debrett’s advice says, to allay any worries they may have had about the evening too.
I agree with pp who says it’s good to reciprocate too, and not accept too much hospitality if you are not going to return it in an equivalent way, like a meal out if you don’t want to cook yourself.