Its a valid question. I'll try to be brief. We do this for a couple reasons:
1. We don't use the Baptismal Covenant term because baptism for us as protestants is a public confession of faith and not effectual for salvation - that occurs at the point of accepting Christ as Savior and King. There are Catholics and others here who believe diffently and I am willing to respect their views onthis matter. However, not everyone who gets baptized are actually believers or completely believe in the Gospel in totality, or attempt to hold their personal standards to it. Baptism means different things to different people, and I blame this on several things not necessarily within the purview of this conversation. All that to say it is the difference in personal theological beliefs and not submitting to the totality of Scripture are the source of potential issues. We deliver the information and answer their questions before they make a decision and well before they sign the covenant. This is only fair to all involved, and greatly reduces future conflict within the Body.
2. It is for legal and church discipline purposes. Within our constitution and by-laws we plainly state with Scriptural references what the standards are, which are only based in Scripture. This includes the LGBTQ issue. We worked quite a bit with Liberty Institute on this to ensure we are not sued for not stating this plainly and someone tries to come in an use the church for gay marriages, etc. This is also fair to those who want to join so that they are fully informed up front that we are following Scripture with respect to what it says regarding this issue (among others) and will not allow it within the body. It gives us the ability to administer church discipline should it come to that (Romans 16:17-18, James 5:19-20 , Matthew 18:15-20 , 2 Thessalonians 3:6, 1 Corinthians 5:1-13, 2 Thessalonians 3:14-15, 2 Timothy 2:24-26, etc), and it has. Fortunately we have not had to do this lately as the congregation is on board with this.
Essentially the reason we do this is to ensure everyone understands that we as a congregation are holding to the boundaries as outlined in Scripture. There are other churches that don't do this, and they are good churches. We, however, are trying to ensure that everything that is going on in the world against the believing Body isn't infiltrating and watering down the Gospel and thereby potentially shipwrecking the faith of others. We have seen how others have barnstormed a church to change them to a more woke agenda. I am rather convinced that what they want is the children of believers, the adults will die off soon enough.
Joining the church is a completely voluntary act. If they chose to agree to lock arms with us great. If they chose not to, we understand and are not going to kick them out of services, Sunday school or anything else. They are fully welcomed to everything we do except be on committees or vote during business meetings. The reason for allowing them to remain is that we are all imperfect. In our church we have some really faithful and very wise leaders that were scoundrels in years' past. What would have happened if someone reject them instead of actually respecting them as they were and having a relationship with them? I cannot help but think that giving others the grace to be with us and be welcomed in is a huge factor in them beginning to understand the love of Christ. Obviously we don't do it perfectly, but giving them the info to make an informed decision, RESPECTING THEM and not rejecting them should they decide not to join is critical to how they view God, both now and in the future. That being said, this love and respect does not cross over into being a doormat to be used by others for their own worldly purposes.
Hopefully I have answered your question.