Because :
1. it is serialized in bimonthly magazine. So only one update per two months
2. Sensei is a slow paced mangaka. That's why sometimes we only get 10 pages per update.
Even with a slow update, Finder is hugely popular. Can you imagine if the update were so fast with a lot of pages? Totally will be the king of yaoi
To add on to #WhoAmI, she produced chapters fairly regularly throughout 2014 and half of 2015 but went on hiatus to work on volume 8. We are all hoping she will return to a more regular schedule later this year, but regular for this manga means no more often than every other month. It takes patience to be a Viewfinder fan but it's worth it.
thank you very much for your responses
Can someone explain why does this manga take so long to update? im only wondering because it is very popluar and it has many fans while other mangas less popular update weekly or at least monthly. Anyone know the the reason?