Though there is no mandate in Scripture to have supplemental services, they served a vital purpose when that was the norm. If you love something, it becomes your priority; it is hard to drag you away from it. The Church as Scripture describes it, is marked by an unmistakable and overt mutual love for one another, and genuine caring for one another. True love desires to be around each other as much as possible. We would call that true fellowship (not what we flippantly call "fellowship" today). I believe that the Early Church automatically had that sense of love and community, and that you did not have to schedule an event to get people to want to be together. Early on, most did not have any designated building they called "the Church", so such a schedule was unlikely to be needed.
Yet, here we are today. Most of us live busy lives in large communities where we rarely see fellow Christians during the week that we worship with on Sundays. I think that supplementary services were scheduled to encourage fellowship, and it was a response to what people wanted. Unfortunately, it may have devolved into being viewed as a forced schedule, and to some... a means of implying who was committed, and who was not. Personally, I liked the supplemental services. I have been in places where true fellowship actually happens apart from a schedule of Church endorsed events; this sadly, was a rare experience.