A built-in license server is not a good options for us because:
it is time intensive. i.e, we have to send registration code manually
it is very easy to crack
it demands us to focus our attention/resources to features which we are not good at (instead of doing so in what we do best)
it does not enable us to keep track of the licenses used/activated
it will be prone to bugs and usability issues as we are not expert in that field.
90% of our users live in US, Europe and Australia, where internet connectivity is not an issue. So, we have to look into our strategic point of view. Besides, more software vendors are utilizing online activation as the pros far exceeded the cons.