From my understanding if growing in any media with salts or synthetic nutes then you definitely need some sort of beneficial fungi & bacteria simply because everytime you add salts or synthetic nutes you are destroying your rhizosphere as you feed the plants directly.
Those who grow organic don't need as much beneficial fungi & bacteria because organic nutes don't kill the rhizosphere & beneficial fungi and bacteria can form & breed from the existing numbers in the soil more successfully.
Needless to say it's still beneficial to add or innoculate your grows regardless of inorganic or organic growing methods because it's a numbers game. Yes soil has some naturally occurring beneficial fungi & bacteria, but not at the numbers you want especially for successful breeding.
Most pgrp products or microbial products for sale are labeled in Spore, prop or cfu & are inactive/dormant. These are decent but also dormant, so if your growing methods include synthetic & salt based then you really kill the majority of Spore, prop & cfu (colony forming unit) before they can awaken from dormancy, establish a colony & breed for numbers. Even if one practices organic methods it is still a chance that majority of Spore, prop & cfu may not develop successfully the first go.
This is where LABS come in to play - live cultures of lactobacillus (lactic acid bacteria).
There is no waiting dormancy period, but once again if using salts & synthetic chemicals then it too will kill even live LABS. Organic growing let's live & inactive/dormant cultures thrive. Supposedly there are certain strains that are more resistant to the harshness of salts & synthetic nutes.
When I grew with synthetic & salt based nutes I didn't bother really with dormant or live cultures because I figured it was a waste of money. Now that I've switched I definitely make sure to inoculate my compost, living soil & feed dormant & live cultures because they thrive with organic growing.
Majority I use are LABS and I make it using jasmine rice wash water & then organic milk till it goes to the curds & whey stage then I separate the whey & mix 1:1 ratio with Blackstrap molasses. Live cultures for super cheap.
Yeah I still use pgrp products like Recharge, Plant Success Organics simply because they were free & work. I usually make a organic probiotic nute tea with EWC as a base, add BioAg Cytoplus, Plant Success Organics, Roots Organics Seabird Guano, Molasses & LAB culture mix tailoring npk ratio adjustment for veg & bloom.. sometimes I add some bunny honey from my rabbit for added nitrogen - heavy in veg & light in bloom. I give this tea every other watering, other than that I feed organic nutes no-till method & various teas consisting of bunny honey & either Down to Earth products or Dr. Earth or Happy Frog. Ive cut my spending down by almost 70% compared to when I used synthetic & salt based. Organic nutes last me alot longer because I don't have to feed as much due to beneficial fungi and bacteria in my active rhizosphere, so its definitely more cost effective for me. For over 10 yrs I grew with Synthetics & salts, then for 5-8 yrs I grew a hybrid mix of synthetic, salts & organic growing. Now I'm all organic & also save my soil to ammend & reuse. I've seen what microbial pgrp products can do vs none & its a huge difference for me in results & cost efficiency.
The LABS were definitely a game changer, as well as researching which fungi & bacterial strains do what like some are nitrogen solubilizing or phosphorous solubilizing or potassium & silica solubilizing. Plus the effects of different trichoderma strains. Currently I'm researching Purple bacteria and how that could be beneficial as well. If anyone has any knowledge of Purple bacteria please reach out to me. Thanks.
*Also this is just my opinion, practices & results that have worked for me. In no way am I stating other people's growing methods are inferior. I have grown great weed using Synthetics, Hybrid (synthetic, salt, mineral & organic) & All Organic. Different strokes for different folks. Do what works for you.