Everyone has slightly different reasons but the main generic reason is safety. If you get busy and your mind is everywhere but your BG, the cgm is there to remind you with a beep if you go low or high.
My main reason was safety and security as I have wild BG swings. And, even more now, since I live alone, the Dex G4 helps me sleep.
You are on the younger end of the life spectrum but I would think the baby will give you a real reason for the cgm. I think it is highly recommended during pregnancy and afterwords, you want to be available for that baby. He/she will need to depend on you to have a good BG for his/her safety and security!! Of course, plenty of Moms do fine without the cgm so I am not saying it is a requirement--just a good option if you can get it.
Number of times to test BG: It depends on how compulsive you are about it. Some test the same or more with the cgm. I do not. Repeat. I do not. I do my two recommended BGs for the calibration and then 2 to 6 times a day more depending on my need. Occasionally, i have a wild BG day and check lots more. My endo, who just retired, unfortunately, rarely checked his BG but then he was very, very stable. He uses the Dex G4 also.
Finally, cgms are not perfect. They do not correlate perfectly with the meter. Meters are allowed to be off +/- 20% though many now meet the 15% criteria. So, the meter can also be wrong. The company line is that "the cgm provides trends."
Still, most of us who have them, or at least I do, consider them essential.
Best to you.