It's what some more experienced users want and the companies are following the well-trod path of optimizing heavily for power users at the expense of complexity, only now it's gotten easier to add absurd amount of code to a project. Not necessarily to make it work right. Personally I have some tasks where sessions between one and five days are typical so I appreciate that it's possible.
Experienced in what dimension? I've been using these tools for about a year and coding for 20+ years, and frankly these long horizon tasks are the OPPOSITE of what I want. I want quick iteration cycles so that it doesn't spend a lot of time and tokens building things I need to throw out. I think the people that mostly want long horizon tasks are: AI labs, because they want you to spend tokens, and vibe coders, who are mostly using it for entertainment purposes.