Compatibility and there are a few known bugs which will require a fork in the future, if I remember correctly one big one related to time-stamping. In addition, I would consider the inscriptions and ordinals to be a vulnerability and an improper use of network resources, and just like any open source project, you want it to be addressed. I understand others share different perspectives but almost everyone knows we cannot just lock in on Core 29 forever and leave it at that. Bitcoin is a project which requires vigilance and maintenance.