Short answer, yes.
It is actually a common practice to throttle internet speed.
Throttling depends on limitations imposed by the ISPs. This can include criteria such as maximum data transferred, content being accessed (like video streaming, Netflix), torrent usage or malicious activity. The goal is not be classified under one of these categories.
Sometimes these criteria are defined by pressures of governments in certain jurisdictions. This is the case in China, Russia and other developing economies.
In other countries, like Africa global transit internet is expensive and throttling is mainly an economic measure.