@fclc Two problems here: one is Not Invented Here (NIH) syndrome and the other is empire-building.
Many engineers will choose build over buy. There are many legitimate reasons for it. But it can be expensive, risky, and time (and opportunity cost) consuming versus a premade solution. Rarely is a realistic cost-benefit analysis done. The solution to this is experienced people who can do a real analysis and nip it in the bud.
Many directors and engineering leads want to build their career by creating a team and product. This is selfish behavior and often goes against the best interests of the company. It takes informed senior leadership who are acting in good faith to keep this in check. That’s very rare.