As agreed, it does produce a very conservative dive profile... problem is, that level of conservative diving is not always available to the average diver. Bluntly, many could not use it, even if they wanted to.
Remember, we are in "basic scuba".
You get on a boat going out diving... the boat plans to go to a specific site.. but when they get there, someone is already there, the wind is blowing the wrong direction.. something stops them.. so they go to another site...this one is deeper...you now make your dive.. with say 33% nitrox to around 90 ft....but they used up time going to this new site, so you want the maximum bottom time, and they want to get back for the afternoon run...which leaves a problem.. you can take longer, but your surface interval will be shorter.. or you can dive shorter and have that one hour (but no longer) surface interval. I choose to have the longer dive, with a shorter surface interval...your system does not allow that.
Situation two.. you are a spear fisherman... you see a really large fish and shoot it.. but you get into a major physical battle...you loose track of how deep you got.. you are worn out...what to do now? The computer actually knows that you have been working and greatly reduced your NDL, so you don't add a chamber ride to being tired.
Note: Increased circulation increases your nitrogen absorption.. several laws of physics involved here, backed up by actual bubble measurements...
Your system hopes that it so conservative that you cover this event.. computers can actually adjust for it.
You plan a dive for say 80 degree water, but when you actually do the dive, the temperature at the bottom is 74 (that actually happen last July in the northern gulf)..suddenly, your three mil is not so warm...
The computers can be made to adjust for sudden, unexpected changes in a way that doing math in your head cannot. However, if you have lots of time, are on no schedule, it still works well. Trouble is, that is not the majority of the diving being done..
And diving very conservatively ends up meaning a lot of missed bottom time and lost dives.
I don't think anyone want to get a case of DCS (at least I hope not), but doing every dive with a huge extra safety margin over what is already hugely safe, does not work that well in a lot of places.
Nor are the majority of divers ever going to be doing team diving...nothing wrong with it, just that it will never be more than a small percentage of people.
It's employed by the best divers in the world and was developed by them in the state of Florida. Many of us have used it in both the caves and the Keys. My last trip to Florida found me in a long penetration of the Spiegel Grove. Silent World Dive Center is the best operator for those of us who are DIR, IMHO.
The fact that you do load at depth is why we "Get out of Dodge" at 30 feet per minute and pause at 80% of ATA's/75% of depth where off-gassing begins (50% of depth for recreational dives).
Breathing lighter gases such as Trimix reduces breathing resistance. Increased breathing resistance increases CO2. Increased CO2 increases stress. Stress produces catecholomines. Catecholomines produce hydrogen peroxide. Hydrogen peroxide can trigger seizure. The harder one works during a dive, the more energy is required, the more energy is required, the more oxygen is needed. As the diver breathes a heavier gas like air, the more work is required to get oxygen from it and the more CO2 is produced. The more CO2, the more stress ... the process continues. CO2 is the sneaky culprit that may be responsible for more diverr deaths than originally thought. Divers who are better trained and who are physically fit produce 50% less CO2. Divers with proper training wear the right exposure suits to stay warm - often this may be a drysuit even in warm water depending upon the parameters of the dive.
One thing about bubble mechanics, if you keep the tension on the bubbles longer, if you do take a DCS hit, it is likely to produce smaller bubbles at shallower depths than big bubbles possibly decreasing the severity of the injury.
The greatest advantages is that buddy teams can remain together and they won't have different ascent schedules being given to them by different computers. There is no computer to lock you out and you can always check this method with Deco-Planner or V-Planner. If the software tells you a variable that you think is more conservative, then great. However, those of us who do ratio deco are usually anywhere between a +2 or a +5 (possibly greater) conservation factor of safety when compared to the software and we can stay as long as we have gas reserves.