I haven't yet worked in a shop where I thought they should have spent less time buying products, and more time inventing things. Obviously there have been some library choices that have been regrettable but there is no shop I've been to that has a general cultural problem of not building enough things. (Background enterprise)

But when I have seen someones make an error in judgement, I have noticed that they realize it much more quickly when integrating software then when building it themselves. I suspect because of the attachment that quickly grows for one's own code.