Components must be as conspicuous as to make spellcasting recognizable - narratively and for balance
I come late to the party, but I thought I could give my 2 cents.
If you look at a spell's metadata, you'll find two types of specifications: insight on its workings (school of magic, area and time of effect, ritual casting etc) and requirements (concentration and components).
The manuals explain pretty clearly why a spell the requires concentration is inherently weaker than a hypothetically identical one which doesn't: only one concentration spell can be cast at a time, and attacks and conditions can break it relatively easily, therefore inducing enemies to attack the spellcaster in order to dispel the effects. Concentration limits the enchanter and turn him into a a high priority moving target. Some situations may call for strong spells, but circumstances where concentration is not likely to last may instead encourage less effective solutions that don't need it. You could it's a high risk/high reward mechanic.
Spell components are supposed to bear a similar onus, and render inherently less appealing incantations that need 2 or all 3 of them. Expensive material components are self-evidently costly, but verbal and somatic are often ignored since they offer yet another layer of intricacy and rarely come into play anyway. I've mostly seen reluctance to recur to flashy magic in delicate social situations: exchange of hostages, arrests, audiences with authorities etc, and it makes sense: spells are conspicuous, and even laymen understand that when a guy in the plaza starts to intone a chant while dancing the macarena, they could end up in ashes. Magic is mysterious and therefore dangerous, especially if one doesn't understand its intricacies: I've seen people irl getting paranoid hearing someone in the same room talking in a foreign language, you can imagine that it wouldn't be weird for a bystander to get itchy and change direction or even call the guards at the first sign of spellcasting.
So, what to do when a character invariably tries to cast a spell inconspicuously, either hiding gestures, whispering intonations or weaving them into a seamless dance/speech? Stealth, Deception or Performance checks are a common answer, but I like to add another hurdle: a check to verify if the spell goes off. Whenever the caster contaminates the choreography of a spell for whatever reason -to hide its intentions, it this case- I like to think that it may not work, so what I ask is for a check with spellcasting ability+proficiency bonus; the more seamless, the higher the necessary DC. This way, potent spellcasters can mutter a few words under a cough and a quick movement, while novices trying the same would end up with stares upon them and no magic.
Mechanically speaking, spells are by far the strongest and most versatile asset in the game, therefore their complexity, risks and limitations have an important role in balancing their use against similar alternatives. A rigorous approach on components may hold the party's wizard from resorting to spells as an easy passepartout to every problem -especially if magic attracts some suspicion- and perhaps let other players try less convenient but safer solutions. I can't guarantee on that though.