it's not a terrible idea. It has it's uses. You just have to know when to use it and when not to use it.

For example, to have fast load times and zero temp memory overhead I've used that for several games. Other than changing a few offsets to pointers the data is used directly. I don't have to worry about incompatibilities. Either I'm shipping for a single platform or there's a different build for each platform, including the data. There's a version in the first few bytes just so during dev we don't try to load old format files with new struct defs. But otherwise, it's great for getting fast load times.