Question: why do Christians no longer worship on Saturday?

When the early church was forming there were many Gentiles (Non-Jews) coming to faith in Jesus. They moved the corporate gathering of worship to Sunday's because that was the day Jesus rose from the grave. It was also thought that a pagan form of worship done by the Roman Empire was done on Saturday, and they wanted to not associate themselves with this kind of worship. Many Jews saw this as a way they (Christians) were separating themselves from Jewish tradition, but that was not the intent. The church did not want to be a church divided (Gal. 3:28).

It is believed that some Jewish Christians might have still worshipped on Saturday in the Synagogue and then worshipped with fellow Christians on Sunday's. The New Testament Church began to see every day as a day to worship and not a particular day. The law of worshipping on the Sabbath (Saturday) was seen as specific to ceremonial law of Israel and did not apply to the new movement of Jesus. You can argue if that was right or wrong.

The problem with today is that we don't do a good job of Sabbath. We don't take a full day to rest as God has commanded us to do. Try it. It is a way to reconnect with God and acknowledge we are not God and we are not human "doings", rather we are human "beings".