zahavasdad,
The longer the davening and the more breaks , like between aliyot the more likely there is going to be talking.
I have been to an early minyan where efficiency is the rule – davening is at a fast, “keep it moving!” clip, breaks are minimized, and there is no speech. Shabbos morning davening is usually completed in an hour and a half, and there is a nice kiddush afterwards with plenty of time to catch up with friends. Yet people still talk during the davening!
I think those talking in shul believe in Hashem, and they know what the tefillos are. I think it’s possible that they don’t fully understand how important their tefillos are – that they mean something and have an effect. That, plus a lack of situational awareness and sensitivity to others.