You have may have been part of the church that has more than one worship service. I know I have. Most of these churches have two or three services on Sunday morning with one on Sunday evening, though some churches have opted out of Sunday night service for a change to meet in homes. Over recent years, one new service has becomes part of church life and that is the Saturday evening worship service. There have been disagreements over whether or not church should have them.
One objection to a Saturday service is Saturday is not the Lord's day. Christians have corporately worshipped the Lord together on Sunday so why have a Saturday evening service. I cannot speak for all churches that do or not do a Saturday evening service, so I am just going to give my opinion if a church should have one.
My answer is it really depends on why churches want a Saturday night service. For example, I use to have a couple of jobs in the past where I would have to work on Sunday morning. I hated not being with my church family on Sunday but they never chastised me for not being there. In fact, I would attend the Sunday evening service which was a different sermon from Sunday morning. There are Christians that are currently going through the same thing where there occupation prevents them from attending Sunday morning so they would attend a Saturday evening sermon. All churches that I am aware of preach the same sermon on Saturday evening and Sunday morning so it doesn't feel that you are attending two different churches.
Some churches have Saturday evening services to get the people who would not attend a Sunday morning service regardless such as the party goers and those who think Sunday morning may be a little too formal. Granted, some people feel this may be a watering down of the gospel message which some churches are guilty of doing, but a healthy church will preach the whole gospel and hopeful encourage those attending a Saturday evening service to serve in their church.
Other churches may do a Saturday evening service because of space or other reasons. I personally don't see anything wrong with a Saturday evening service as long as the Bible is preached and Christ is exalted. Should every church have a Saturday night service? No. I know my church will not have one because we are not a large church, though that might be one thing to look at if we grow, but that is just speculation on my part. Every church should seek what the Lord wants for them and He may not even lead your church to have a Saturday service or even multiple services. However, we should not judge a church that is gospel-centered when they have a Saturday night service.