Mainly because they are only useful against certain factions. Too limited to be used over things that work against everything or simply buff your survivability in general.
And that's not counting how much mod space is filled by mods that affect power duration, strength, ect. Add in Redirection, Vitality, Steel Fiber, ext & you'd be hard pressed to find space for any of those mods you mentioned.
In most of my own builds, I rarely have a free spot. Though when I do, it's Handspring. :D
Adding one of the elemental resistance mods would be nice but usaully they just lose out in a veritable ocean full of good mods.
Redirection, Vitality, Steel Fiber, Vigor, Streamline, (Primed) Continutity, (Primed) Flow, Intensify, Stretch, Rage, Quick Thinking, Equilibrium, Constitution, 5 Corrupted Mods, at least 2 Augment mods and of course the people that use Rush. Then less comonly you still have Handspring, Surefooted, Fast Deflection and Fortitude.
So you end up looking at 21 to 26 mods that people would pick before putting on the elemental resistance.
As well, the elemental resistance mods provide at most 60% reduction of a very specific damage source.
- Flame Blades, Scorchs, Napalms, Sargas Ruk and Lech Kril can inflict Heat damage
- Sniper and Prod Crewmen, (Corrupted) Nullifiers, (Corrupted) Vor, Electric Crawlers, and Arc Traps do Electric Damage
- Toxic Ancients, Lobber and Toxic Crawlers, and Mutalist Ospreys do Toxic Damage
- Lech Kril is the only Ice damage
- Detron Crewmen and Death orbs deal Radiation Damage
Almost all of these are low hazard due to being rarely spawned, limited to specific locations, easily avoidable and/or bosses. Toxic Ancients are about the biggest hazard on the entire list due to the properties of Toxic damage.
Simple conclusion; the effectivesness is limited, it's a minmal gain and you lose a mod slot.
Nothing except lanka does electricity damage. Nothing important except grineer napalms does heat damage.
Most people find it easier to dodge a few attacks than to sacrifice an important mod slot.
Warm coat does.. absolutely nothing. in all situations, including the extremely rare ice levels (the only time it does anything more than waste a slot, vigor is several times better).
With warm coat, you loose 38% instead of 50% of your shields in ice levels. instead you could just use vigor, and have more shields in the first place, in the other 97.5% or so of non-cryoleak missions.
Yup, it's just way too situational for me to ever use something like it. Hell, I can't even be bothered to put on the "Bane of bla" mods on my rifles or swap my elemental damage type to fit the enemy faction because I want to have one build that works kind of for everything.
Not the most efficient against anything, but as a result I have the benefit of not having to swap my builds all the time.
I do hope that DE will make something out of these resistant mods, maybe next we could have resistance mod slot which separated from our ordinary mod slot. Let's say, 2 res mod slot, so we could combine resistance or 1 stronger single resistance. This will make these resistant mod useful. And as far as I know, each of elemental resistance is still not super OP as they have their own weaknesses. So yeah, having separate resistance mod slot is a good idea DE should do next.
Another player asking for a game-breaking mod that would be a must-have on EACH AND EVERY SINGLE BUILD EVER, would single-handedly distort the economy and would increase even more the problem of power-creep.
Because higher would be game-breaking. And the uber rare drop rate would mean in either high demand, so pricey, or no one would find it. Also DE could try and sell it in a plat or money only pack. Smart, eh?
Not really. 60% resistance to all elements is an infinitely scaling buff to your frame. It would be absolutely essential in each and every endgame situation and vital for absolutely every single build. So players would either farm for it like mad, and get frustrated by the uber rare drop rate, or would pay a fortune for it - and if it's really that uber rare, it would actually have a seismic shift in platinum prices on the open player-to-player market.
And if DE makes it available for plat as the only realistic way of getting it, most players would probably be outraged as this is about as close to P2P as they can get.
There are times when they are, however, useful. Today's final sortie was a survival against the corpus where everything was on fire. I took off one of my pare mods, soloed it for less... actively aggressive enemies, (wall to wall nullies and sapping osprays ontop of everything on fire) and put flame repellant on my Loki. I was able to survive it thanks to taking less fire damage from the environment.
It was a last resort as I didn't want to use it... but yeah.