In case you did not know every 3db cuts the signal in half so 6db is 1/4 the signal at the antenna
While this is true, it's not anywhere near the whole story. The amount of signal your radio gets, while is important, doesn't matter much once you get past a certain level and once you reach another level, you have too much signal and will start having issues. Anywhere in that large area between those two levels you're good. Now I can't just tell you exactly what those two levels are, they depend on your exact situation (radio, type of system, amount of RF "noise" in your area, etc.).
It's kinda like saying that you really need a 100 gallon gas tank in your car so you can drive to your destination. So long as you have enough to have it flow properly from your tank to your engine, any extra in the tank (beyond a safe margin you need to make it to the next filling station) is just extra weight you're carrying. Sure you need a tank large enough so you're not stopping at every station you pass, but beyond that it doesn't matter that much if it's a 10 gallon or a 100 gallon tank.
If the system you're trying to pick up are very strong at your location, the coax loss really doesn't matter. You can afford to get 1/64 of the signal at your antenna and still pick it up just fine. Now if you live in a rural area and are trying to pick up a system that's a very long distance away, you may need every microvolt of signal you can get. Chances are you wouldn't notice the difference between that cheap RG-6 and that expensive LMR-600 for normal scanning. Well, you'll probably notice a few differences, such as cost, ease of installation, etc.