Not making excuses for every instance but in the vast majority of cases, optimizations are done by making trades between runtime performance, RAM usage, and disk space. Of these, disk is cheapest. You might optimize something and end up using more disk space as a result.
For example not all video cards support compressed texture file formats (though gaming hardware is likely to be close to 100% now…) so you might store texture memory uncompressed on disk (bigger size) to save on the decompression needing to happen on the CPU before transfer to the GPU.
points taken, but what I meant was that they of all people should be able to make the best possible game on their engine. if they were making the game on a new engine it’d be easier to understand if their eyes were bigger than their stomach due to their inexperience