My guess is that this trend comes from investors who are sick and tired of looking at pitch decks, especially poorly done pitch decks.
As a pitch coach, my experience is that the first thing investors ask for before offering to have a formal meeting is to see your pitch deck. It's a reality check for them and a marketing doc to interest their partners in coming to your pitch.
Even if you didn't need to send a deck ahead, I think it's a very bad idea to present *anything* without visuals. People take in information and learn in different ways: some do better when they can read, others when seeing visuals, and others by listening. Usually, it's a mix of all 3 but, for instance, if you pitched to me, a very visual learner, just by talking, chances are that I'd miss important information.
Assuming, as Andrew Lockley said, that you are doing more than an informal elevator pitch, you need a deck. You never know how people learn when you are first pitching to them, so having no deck, i.e., no visuals nor writing, is a risky move, IMO.
You are also making your life more difficult in the long run: If you are going to pitch without visuals, then you have to have memorized your pitch - which is always a good idea. If you don't, the chances of your forgetting important ideas is very high. Heck, that happens all the time even with well-prepared decks!
Finally, when I am retained to develop a pitch (visuals and script), I invariably find that creating the visuals forces me to be more accurate in telling the story than when I just write a script.