This approach can work for experienced speakers, in particular if you have spoken about the given topic before, but I'd strongly advise against not rehearsing for folks a bit newer into their speaking career. So often I have seen talks where folks either were time after half of their time slot, or they ran out of time towards the end. Or they lost track of the plot, went off on a tangent for way too long, etc.

All this is not great for the audience (who have "invested" into your session, by paying for the ticket, spending time away from work and family, not attending other concurrent sessions, etc.), and it can so easily be avoided by rehearsing.

The most common reason I have seen for folks skipping to rehearse is the awkward feeling you might have when speaking loud all by yourself. If that's the issue, it can help to do a dry run in front of colleagues. In any case, "winging it" is best reserved for later on, after having gathered quite a bit of speaking experience and having spoken about the same, or very similar, topics before.

I'd also recommend to avoid reading from slides during a talk as much as possible, it's also not a great experience for the audience. There shouldn't be much text on slides to begin with, as folks will either read that, or listen to what you say, but typically have a hard time doing both at once.

(All this is a general recommendation, not a comment on your talks which I have not seen)

After I finished my "industrial year" at university, we were all asked to give a short presentation on what we had done "in industry".

Returning to university after my industrial year, I took a very dim view of the academic environment and resented being asked to do this task that was worth no credit towards my degree.

So I didn't rehearse or even make any slides, I just stood up and talked about what I had been up to.

And although I was by any measure an extremely inexperienced speaker, it was the best talk I had ever given. It was the first time I stood in front of a room of people and felt present in the environment while giving my talk, rather than monotonously reciting the rehearsed material.

So obviously different people have different experiences, but I learnt that day that rehearsing your talk isn't always helpful.

It helped that I really enjoyed my industrial year and had loads of interesting stuff to talk about. So maybe the more important thing is to be interested in the topic.

My father, who never did any public speaking, and as much an introvert as you'll find, did this for my wedding rehearsal.

I was amazed at how naturally and well he did. All he wrote down were 6-7 topics to talk about. He got a huge applause.

I have to agree, if it's clear the talk is just someone mindlessly rambling about a topic, it leaves me feeling like my time isn't being valued and I don't know why I'm spending it listening to this person.