Mostly title inflation. Using GPT API does not make you an "AI engineer". I don't even know if anyone would seriously call themselves this. Usually they are either software developers that actually work at an AI company or a researcher. The others are mostly fake jobs.

I'm pretty sure people suddenly had BS like "Blockchain engineer" in their linkedin headline in 2022.

Edit: https://openai.com/careers/search/?q=Engineer Most jobs involving engineering don't even have AI included in their title at OpenAI, though they do have Applied AI engineers and AI support engineers. I highly doubt these other companies suddenly have a huge growth of AI engineering jobs available.