Because once you’re at the max you’ve been painted into a corner when tolerance kicks in. If you’re at a lower dose you can increase. If you’re at max dose you can either start stacking or exceed max, but that’s about it. So prob best not to rush to an unnecessarily high dose.
Tolerance to GLP medications is not really something that actually happens.
What people think is tolerance is usually the effect of weight loss, after a while of being on a dose of GLP you have lost weight , as you lose weight hunger goes up and metabolic rate goes down, so you stop losing weight and are a bit more hungry. But if weight is stable at that new point and not increasing, that is the drug doing its job, it has just done as much as it can in you at that dose.
If tolerance was real, and all the scientific studies say it is not , then people on these drugs for years would start gaining weight and every study says weight goes down for about a year then stabilises at that new lower weight and stays there for years ( I think 3-4 years is the longest follow up so far ). Assuming you continue on that dose.
Nearly everyone on these medications will get to a point where weight loss stops, hopefully this happens at a weight you are happy with, and at a dose that does not cause too many side effects, but how slow or fast the doses are increased , are not going to change where that point will be, that has more to do with genetics , lifestyle , exercise and diet, and the dose of reta you are on at the end. And to keep the weight off, that is the dose you are likely to need to stay on , assuming you are no longer losing weight at that point.
Whether staying on low doses as much as possible is a good idea , I think , depends on what you want from them. If you are younger and 10 kilos overweight good idea, average weight loss from 1mg of reta was nearly 9%.
If you have a BMI of over 35, and especially if you are older or have obesity related medical problems - metabolic syndrome , hypertension, heart disease, diabetes, high cholesterol etc. then I do not agree with the low dose approach. If you are losing weight at a rapid weight on a low dose, great there is no need to push the dose, or if side effects are a problem, but if you have a lot of weight to lose or weight loss slows or stops then increasing to the standard maximum dose of 12mg for reta is what you should be aiming for. It has been proven that higher doses are more effective than lower doses for preventing diabetes and heart disease, not for reta yet, but for semaglutide and tirzepatide, and though not proven yet it is very likely that this will also apply to reta. And obviously higher doses are more effective at causing weight loss, most recent longest term studies on reta show an average of 29% at 12mg which is amazing.