Should I have ALL the exterior paint scraped?

I have a house from the early 1900s so it probably has multiple layers of paint. I’m getting mixed opinions with some Painters recommending to scrape ALL the paint off before painting and other Painters recommending only to scrape the parts that are flaking/coming off and that the original paint actually protects the wood.

Note: the parts that are flaking off are in areas where it gets hit with direct sun.

What do you think?