T1 guarantees a level of service not a fixed speed. Your 100 Mbps connection at home is only averaged, and on most days it is a lot lower. Take a speed reading at midnight vs 5pm on the weekdays, or basically any time on the weekends. As a consequence your home connection shares bandwidth. If your neighbors both simultaneously decide to binge watch every Game of Thrones episode while downloading the latest games and playing on their cell phones you will suffer a pretty noticeable decrease in QoS.
when market opens, my neighbor is working in the office, so few people share bandwidth with me.
