By my best understanding, the twice-a-day rule is in place to accommodate people who attend a regular daily Mass every day, on the days when they also go to a wedding or a funeral, etc.
The second time is not generally supposed to be the exact same Mass as the first time, but if there is a special reason (someone is getting married, someone is being buried, a relative is receiving a Sacrament such as First Holy Communion, Confirmation, or Holy Orders, they can still participate in Holy Communion at their relative’s special Mass, as well as the regular daily Mass that they attend.
We all have plenty of daily tasks that we must attend to, and although it’s a very good thing to be a daily communicant, being a twice-daily communicant has the potential to interfere with one’s duties to one’s employer and family - one must keep a proper balance in life.