Here, i cannot really see reasons not to use a library which requires linking.
There are much more people using only header-only Boost headers. The same as above.
It might be even worse. If *existing* libraries will start using Boost.Log in an update (because it is really useful), existing project files and solutions will be broken. If an existing header-only library starts using the Boost.Log library we'll need to update the makefiles. This is a reasonable cost. In reward we won't need to compile the Boost.Log lib over and over again.
All your statements are based on your opinion that linking is no problem, whereas all my statements are based on my opinion that linking is a problem... So I think we stay keeping different opinions here. Regards, Barend