It is easier, but it can be considered as feature-bloat if you don’t really need the breadth of capabilities that it offers. Aside from that, OpenBSD has made specific choices to make it more secure than FreeBSD by default, though the configuration will depend upon the user.

It’s also more fun to DIY it and you no longer need to rely on a specialist version of BSD. You are closer to the source, so to speak.

Some reasons might just be philosophical, others can be technical if you have specific configuration that you’d want to achieve.