I would generally agree that there isn't much of a reason to worry about company formation until there is an idea that you have has shown has some viability.

Otoh, for some incorporation or forming an LLC is a demarcation point in their thinking that they have something "official" and a certain level of seriousness about what they are doing.

While someone can easily hack together a website over the weekend (as the meme goes) having to put some effort into business registration, accountants, possibly attorneys and trademark registration seems to make some believe believe they are taking the first step toward something they are committed to and ties them up at least a little from walking away (consistency principle). Many things in life work in a similar way (marriage comes to mind as only one).

This is a relatively new phenomenon as starting a business before the internet generally required quite a bit more money (the commitment) as well as possibly renting a physical location or at least placing advertisements in the local newspaper or yellow pages. Even getting phone service was expensive.