This has been true in Resident Evil games for as long as I can remember playing them as well as a few others that mostly are also survival horror games.
I finished Biohazard / RE7 yesterday and when I got to the end I had a ton of ammo in my big weapons because I had been saving them for more difficult fights even though it could have made my progress a lot easier if I had used them during regular gameplay.
I am one of those gamers that tries to use my "pea shooter" as often as possible even if this means that the fights are going to be more difficult. I kept putting all of my shotgun ammo in storage, rarely using the machine guy, and i NEVER even saw what the grenade launcher looked like because I never used it once. :)
Rather than bamboozle the above standard enemy with a shotgun blast to the face I would back away, make a headshot with the standard handgun ammo, wait for their invulnerability animation to go past, then crack them twice more until they dropped (it only takes 3 shots.) I would have obliterated multiple enemies with one remote bomb, but I was "saving" those for more difficult encounters.
Just like so many times in the past, I ended up having many remote bombs, all my grenade launcher ammo, and most of my shotgun ammo in inventory by the time I finished the entire game.
There was one particularly tough boss battle where you are fighting two of this enemy called "Fat Molded" that was the only boss that I considered worthy of my big guns where I used my remote bombs liberally and that was just a one off. It was extremely effective in taking them out super quick.
These guys will take a ton of handgun shots to the body or head and in my first try against 2 of them at once I just got worked since they have a ranged attack where they puke all over you and cause rather high amounts of damage.
Since I already knew where they were going to spawn - which was quite close to one another - in the arena the 2nd time I got to them after a massive reload, I just placed a few remote bombs next to where they first climb out of hte ground, then detonated the bombs and finished the job with a few blasts of the machine gun. It was absurdly easy once you understood that you could do this.
I made similarly quick work with the final boss in the game which I kind of believe is intentionally a pushover boss anyway. It spawns in the wall of a room you are in and you won't know where this is going to be the first time you get to it but once I knew I just repeated the process and detonated remote bombs again. This resulted in a fight so quick that I didn't even have a chance to detonate all the bombs before it did an animation sequence to take you to part 2 of the fight.
The moral of the story here is that when you have big buns and ammo, particularly in the latter half of the game where there are a lot of enemies as well as a lot of ammo drops, you should go ahead and use it. I think I actually made the game a lot more difficult for myself and probably less fun by attempting to take out everything with the weakest weapon you have in the game. Unlike other RE games I have played in the past, they aren't as stingy with the ammo in Biohazard as they have been with other games, so go ahead and use it.
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it is incredibly satisfying to stick a remote bomb to an enemy then run away and detonate - plus you get a reward trophy called "it's a spicy meat-a-ball!"
Since Biohazard allows us to make multiple save points I think a wiser strategy to take would be to make a separate save game where you make the choice to change over to big guns and that way you can go back and redo it if you went too crazy with your ammo usage. Honestly though, they hand out enough ammo in the final two stages of the game that I don't believe that this is going to be a very big issue for most people.
So go ahead and use that grenade launcher, I think you will make your gaming experience better by not saving it for a rainy day that never comes.