[jrochkind1]

I mean, if you know what you are doing because you have made for instance BBQ many times before, especially even on the same equipment, it's not exactly "completely guessing".

People did make good BBQ for many years before digital thermometers existed, and without using meat thermometers! I suspect professional experts barbequing all day probably still don't use thermometers. They are have the same heat source many times, and know how it cooks and know how to judge the size of meat, because they've done it hundreds of times.

But yeah, for those of us who are less expert, a meat thermometer can get us much better results.

[xeonoex]

You can go by feel and sometimes appearance (and pretty much have to for some things like pork ribs), but the size and shape of large chunks of meat vary quite a bit, so does the weather, heat source, etc...

If you're a restaurant that is constantly smoking meat, you probably don't need a thermometer, but you probably have one. If you're an ordinary person, I would recommend a decent one at least. I have a thermapen. I don't regret buying it. If my fire dies and I don't feel like chopping more wood, or if I just put the brisket in the oven to finish overnight after it gets smoke, I can still know exactly when it's ready. I don't have to repeat the exact same process every time for a good result.

[Arelius]

Sure, if you have the same heat source, in an environment with the same atmospheric conditions, working on a piece of meat similar to what you've cooked many times before, you likely don't much need a thermometer, not that it'll hurt.

But a thermometer let's you transfer those skills much more easily to environments with varying conditions, It's especially common for professional cooks to be expected to cook in varying conditions.