^ A bit of deposits on the intake manifold past the throttle body are not a problem unless it's fouling a sensor or some other (idle control perhaps) valve. On the cylinder intake valves if it's not direct injection you have the fuel injectors (or carb going back decades ago) external to them, cleaning them off and reducing buildup rate due to running cooler from the flow of fuel past them. You might have to clean your throttle body too once on a blue moon but it's not the only source of deposits, you still have EGR.
If you have some bolt on (external) sensor or valve, it can be cleaned later or replaced more easily and inexpensively than adding a catch can and monitoring, emptying it periodically. It could also result that on some engines a catch can is going to reduce crankcase vapor scavenging (which keeps oil cleaner) rate so for equal protection your oil change interval may need to decrease. That can also cause higher crankcase pressure which reduces engine efficiency. Engine tune and piston rings can expect a certain PCV flow rate and crankcase pressure range.
In other words, of things people bolt onto engines, there just hasn't been significant enough benefit for a non-DI engine and some drawbacks. Consider those who design the engines, granted their designs cause a problem on DI but the non-DI engine has been around for a long time.
If the catch can had a cost effective benefit it would be on the engine already. If it were even the best solution for DI engines the manufacturers wouldn't be looking at ways to add an additional external injector instead of a catch can.
I have a problem with my vq37vhr (naturally aspirated V6, non-DI) engine with 105K miles on it. The issue is not major but rather annoying. RPM drops below the nominal idling value (650
± 50) for a split second at a hard stop after some highway miles. The car shakes at that moment but immediately picks up the revs.
I have been on different forums trying to understand the engine dynamics (that I thought relative to my problem) a little bit better since no CEL. Forum members indicated that this problem was inherent to some vehicles even after 30k miles. The majority of the forum community recommends cleaning the throttle bodies (TBs) which solved the problem for the most but not for everybody. Cleaning the IACV fixed the problem for at least one case. I have never been able to solve an engine problem with an easy fix since I am extremely lucky.
Neither of the methods mentioned above solved my issue except warming up the engine to operating temperature before taking off. This method had eliminated the problem for me for months until a couple of weeks ago or so. The dealership looked at the issue and performed the idle air volume learning procedure. This helped with the problem a little bit as the rpm has not dipped below 500 revolutions at a hard stop as it used to. However, this did not fully resolve the issue. There is still a slight dip at a hard stop but occurring intermittently. Subsequently, I cleaned the IACV (idle air control valve) and it has a little to no effect on the problem. This was the time I realized my intake manifold is extremely oily/greasy. Every port/nozzle on the intake manifold shows signs of oil coating on those ports once you pull the respective hose. That made me learn about the PCV and it's functions, catch cans etc. Catch can idea made sense until I read your post. Also, one of the problems that the dealership found was with the fuel damper. It is noisy like a diesel but only if you are in the cabin. Fuel and air are the main components of the combustion and I changed my spark plugs less than 25K miles ago which is half of the recommended interval. I ordered original PCV valves, fuel damper and IM gasket. I will replace those and clean the IM and the TBs hoping that the issue will be resolved however, I am not optimistic.
I do not even want to think about this problem may be related to oil pressure drop due to the faulty oil galley seals in this particular engine. As they were made out of paper for a certain period and were replaced by the metal ones after problems arose but the manufacturer never made a recall on this because the galleys are behind the front engine cover and the timing chain, tensioners etc has to come off.
Any input is appreciated and thank you for your time.