In 1969, Pope Paul VI prohibited communion in the hand (in Memoriale Domini). Within a few years, widespread disobedience to this command led to him giving in and allowing permission to be given on a limited basis for this practice. I will not judge anyone about this, I was not there and do not know all the factors; I merely refer to the historical event. In 1980 Pope John Paul II (in Inaestimabile Donum, 18) said "women are not permitted to act as altar servers". Within a few years, similar disobedience to the above situation also caused a change and Canon Law was reinterpreted to imply that girl-altar-boys were allowed. This is how changes (bad changes especially) are able to be snuck in the back door.
Having raised five children, I have seen just about every attempt to "wiggle" out of the rules. Often children know exactly what the rule is, but they try to ignore it. Sometimes they will just do what they want. Other times they try to stretch the rule ("you never said not to kick my brother in the head, you said not to punch him in the head!"). It is common for children sneakily to repeat a disobedience behind closed doors and hope that it does not get noticed, and that if it does, the parents will be worn out from trying to change the behavior and will eventually just give in. This is bad when children do it; it is horrible when adults do it.
When someone really wants to pressure someone to change, there are many methods to do so. The most effective method is to sneak the change in by disobedience, and then make the person think that the change was his own idea. Whenever someone switches his position on something it will always have more lasting effect if he thinks that he chose to change, rather than if he believes he was coerced. The most effective method of this is obvious: repeat a disobedience until they get used to it.
This is also how Mass done versus populum (the priest turning his back on Jesus) was snuck in the back door. It had been happening for years in Europe, eventually worked its way over to America, and finally got "grandfathered in" (no actual permission was ever given for this, and the rules in the Roman Missal 3rd edition still presume that the priest is facing the altar when speaking to the Lord!). This is quite a remarkable thing when you think about it. This means that no allowance was made for this behavior; thus, every priest is technically not following the Church's rule when he faces the people for the entire Mass (!).
In my desire to be faithful to our Catholic traditions, while navigating the tumultuous waters of modernist attacks, I often encounter various rules being broken, and find that I need to correct people. I must say (in case anyone doubts it) that I really do not like correcting people. In fact, my regular temptation is to avoid the correction as long as possible and hope that the people repent on their own. Yet, I know that this behavior is not what I am called to (and I will have to give account to God someday for how I ministered as a priest). Therefore, I grit my teeth, clench my fists, and speak to people as gently as I can.
When these encounters of correction come up, I find, more often than not, that people respond with an attitude of "what's the big deal? its only a little rule I'm breaking". No, they never actually say that, but that is what is clearly being said between the lines. I will tell you what the big deal is: bending a small rule makes it easier to bend a big rule, and once we start bending the big rules, we will next make it a permanent habit to break them. This is what has been happening in the liturgy over the past 50 years (as I said above). If we are going to find a way forward from this chaos, then we have to stop breaking the rules. We have to begin where it matters the most: in the Mass. We have to start doing exactly what we are supposed to do, and seeking joy in obedience.
This is why I like my "i's" dotted and my "t's" crossed. Not just because it is what we are supposed to do, but because it is for our own spiritual good, and thus it is for the spiritual good of the whole Catholic Church. So the next time you see a priest obeying the rules of the Mass (which, as laity, you should know what those rules are!), give thanks to God. Pray for that priest, because he is probably under attack for it (even if only in a spiritual manner -- which can also be very painful). Pray also for those priests (and laity) who continually disobey and seek to encourage others to disobey; pray that the Lord would grant them penitence. Pray for our Pope, and pray for the Church throughout the whole world. May God have mercy on our souls.