That point aside, we are talking about "opportunity", not the same as risk management. The swing on the maul offers an "opportunity" you might not take it because you want to save it for counterspell, or shield or maybe you are a PAM and you are waiting for that other enemy to enter your reach. At the end of the day swinging a Maul offers more "opportunity" to attack someone than casting a spell RAW logically should.
I'm going to have to offer a point of disagreement here.
Let me point out that the following applies only to wizard spells (I'll explain why shortly). Wizard spells are the result of study, and in order to tap into the magic that powers them, Wizards need to follow a certain formula/recipe/rote execution that allows them to unleash and direct magic energies (sorcerers have an innate "feel" for magic, clerics spells are minor divine intervention, and otherwise do not seem like they would be dependent on executing the formulaic actions a wizard must do to trigger a spell).
Verbal components might not be subject to disruption by an attack - but a silence spell should put a halt to them and of course if I am grappling with a wizard and he starts chanting esoteric words, I should think holding his jaw closed or jamming my fingers in his mouth would be sufficient to spoil the proper pronunciation of the syllables he needs to pronounce in order to trigger the magic.
Similarly, swinging a weapon at a wizard using somatic components to cast a spell forces him to either dodge my attack, thus spoiling the careful pattern his body must move in to trigger the magic, or allows me to hit him, and the force of that blow will itself spoil the careful pattern his body must move in (e.g., if he needs to sweep an arm up and my sword's downstroke catches that arm at belly level, that arm is not going to be able to complete the upward sweep).
A material component or a focus could be fumbled when trying to dodge a blow or knocked away on a successful hit.
Finally, it is a long-established fantasy trope that the archvillian is trying to complete a ritual to cast a powerful spell. It strains verisimilitude for me to think that a "regular spell" is anything other than something
exactly the same as a ritual in all ways except scope (taking fewer words, motions, components, and/or time to cast).
I think letting spells go automatically is absolutely the most immersive, no contest.
So, IMO, letting spells go automatically absolutely breaks my immersion
every single time, no contest.
HOWEVER - as I mentioned before, a sorcerer (who derives magic from an inward source and does not necessarily rely on a rote execution of words/actions) does make sense as an "automatic caster" to me. A warlock or a cleric, whose spells are minor interventions from greater powers rather than triggered by the character's learning, is also something where I can see magic not requiring them to do things (though I would submit that this sort of spellcasting could also be viewed as triggered by a minor verbal prayer for intervention, or the execution of rituals of devotion with the body and/or items such as burning incense and thus would be subject to disruption the same as above).
Also, all spells relying on concentration to maintain? It makes it immersive to me to think that such concentration can be broken.
So now the question becomes not one of verisimilitude, but rather of game balance - it is not balanced for some casters to be "automatic" and others to be "subject to disruption." Some editions of D&D have elected to make "all casters subject to disruption." The design choice for 5E was to "make all casters automatic" - that DOES have the virtue of allowing the characters to use their fun abilities instead of having the buzzkill of watching a character lose their fun abilities just because they got hit.
To me, it's on the same level as "Counterspell" and I have this discussion with my players in Session 0. "Counterspell" (or whacking an opponent and disrupting a spell) feels AMAZING as a player when you do it to the big bad. It feels much less amazing when some toady does it to your character. And in my campaigns, what's sauce for the goose is sauce for the gander. I discuss this in Session 0 with my players, making sure to note "let us decide now whether or not Counterspell and Disrupting a Caster are a thing, but be aware that if they're going to be a thing for you, they will be a thing for the bad guys too." So far, none of my groups has wanted either one to be a thing because they don't want to risk their cool stuff being countered (my personal preference is that they both ARE a thing, but this is a choice to make as a group, not by DM fiat).
So there's my two silvers (I wrote way to many words for it to be coppers).