Shrink wrap was the most accurate at the time, especially accounting for reptiles, which were the original inspiration for said technique.
And since most soft tissue doesn't fossilize, they were doing the best they could with the tools they had.
And while they were often wrong, I would like to see you try to guess what the animals looked like, based on skull alone, and compare your accuracy against the people you're calling lazy, probably from the comfort of your own toilet.
Not to be a dick but,