therefore such a plugin would increase the use of Limesurvey as well.

There hs been a Wordpress plugin in the past, but I think it never really took off. And to be honest, such a Wordpress plugin would most probably mainly attract people that want to use the community version of Limesurvey and the core developers won't make any money with that. So at the end, it is just natural that the resources are focusing on LS itself, not a plugin to Wordpress. That being said, there are independent developers out there, that can create such plugins. But they also need to see some advantage for them. Either monetary or for their own projects.

I was thinking of people having a simple Wordpress hosting plan, but also wanting to use Limesurvey for their site/services.
Instead of hosting and maintaining everything themselves, they could just buy a hosted Limesurvey plan as well, if the integration of users/participants wouldn't be a problem. But i guess you're right, that market is probably not big enough.

That market surely exists, but there is a lot IFs and WHENs. And then there is another hurdle.

Limesurvey developers are surely good in Limesurvey and Limesurvey addons/plugins. They probably have little to no experience in Wordspress plugin development. So either they need to learn this or they need to hire someone.

I think developing a Wordpress plugin would make more sense from the "Wordpress" side. I mean, you need to understand how the Limesurvey GmbH makes money. I have no deep insights, but I think their main stream of income would come from the SaaS offer. Then there might be some money coming in from the Comfort Update as well, but that's about it.

So they probably mainly focus on these things. To be honest, I haven't seem many new (important) features over the last couple of years, despite the changes to the UI. Considering that today a lot more developers work on Limesurvey I find the progress rather slow, compared to 10-15 years ago. But that might also only be my impression.

I hope that for LS 7 we see a focus on improving Limesurvey feature wise. The "UI experiment" (and I was one of those that thought it was important back in the days) hopefully is drawing less ressources from now on.

As we said before (Jelo also provided the links), there was a third party plugin called Surveypress and the Limesurvey GmbH took over at one point, but this never really went anywhere. Maybe it can be revived?

And here something Denis has built:

extensions.sondages.pro/admin-authentifi...dpress/documentation

But of course, this is a Limesurvey Plugin, not a Wordpress Plugin.