I agree with you that it would be nice to have the full 2017 schedule already visible. However there are two issues for me:
1) maintaining the calendar manually takes time and I don’t want to spend a full day just doing it
2) many of the small local (volunteer-based) conference don’t provide information early. This is why we try to have only a 2-3 months ahead updated schedule for the current year… and sometimes we are late in our update ;O)