If I could add to some of the thoughts already expressed --
It isn't just the Watchtower that uses that set of verses in such a manner. It is a favorite of pastors used to tell people of the need to regularly "go to church".
There is a specific purpose for gathering together and the writer of Hebrews tells us it is to "spur one another to love and fine works" (v24) and to provide mutal encouragement. (v25)
Unfortunately the atmosphere at the local Kingdom Hall is typically not marked by the love that Jesus displayed and requires of those who claim to follow him. The Witnesses boast that they show "Christian love" by not going across the ocean to war and killing their brothers. How tragic that they invalidate such a stand by not showing love to the person across the isle, even harboring hatred! The elderly among them readily will testify of the chronic lack of love that permeates the Organization and grows colder day to day.
Further those verses do not say when and how often and in what manner ones should gather together. For many years there were meetings at the Kingdom Hall on three seperate days. If a person only attended two of those days - it would be said that they weren't following this counsel. What now? Today, there are only meetings on two days, and that same person in now in full compliance! Early Christian meetings were real interchanges marked by love and mutual encouragement. It wasn't sitting in a chair or on a pew and staring at the back of someone's head for an hour or two before rushing out to the nearest lunch buffet. Some Christians find much more love and encouragement meeting together with two or three for coffee than "going to church" or the Kingdom Hall.
