It's a tool designed for professionals. Professionals operate with standards, so in a professional kitchen in America, you will never, ever need or want to read a temperature in Celsius. In the rest of the world, nobody will ever use Fahrenheit.

Having a button that changes it with a single press is actually an impediment to working quickly, and only introduces uncertainty and anxiety about the tool. Measuring temperature isn't like measuring weight - seconds matter. A moment of confusion could be enough to ruin a process, and a failure to notice the change in settings could create a dangerous situation. Nobody wants a button to see the wrong number.

Think of it like compile-time config. It's there, you can change it if you want, and everyone will have a preference, but if you need to change it often, you're not the target market.

In the rare consumer case in which you may be using foreign measurements you can change it once at the beginning of the recipe.

This idea that because a commercial kitchen doesn't mix F and C and thus nobody else should ever have to is ridiculous and is a form of gatekeeping. I download recipes and measurements are sometimes F, sometimes C. Sometimes ounces, sometimes grams. Sometimes cups, sometimes mls.

I think if you could need to change it occasionally, you could easily be in situations where you change it frequently.

Shadow kitchens that make recipes for multiple different restaurants could have measurements in both.

To not have the button at all would make sense(compile time config), but if there are situations where you need to change it, those can come up as frequently as every time you use it

No.

Every commercial kitchen complies with and is inspected for compliance with food handling regulations.

Any recipe in commercial use is written specifically for the kitchen in which it is made. One might even consider them a complete vertical unit: if the recipe is designed as a chain or franchise standard, the kitchen standard is designed in tandem to match.

You will not find a commercial kitchen in America using Celsius for anything.

If you don't want professional tools don't buy them.

It shouldn't be difficult, but it should be foolproof. Someone not paying attention could mistakenly get a Fahrenheit reading expecting Celsius, and serve undercooked food to others.

In food applications, I should think that even the most hopeless cook can tell the difference between 75 degrees F and 75 degrees C. One is cooked and the other is room temperature.

I have very cheap 0.1g precision scales and reasonably cheap 0.01g precision scales.

Tablespoons (for example) are often equating to 10-25g which even the cheapest, nastiest 1g precision kitchen scales can handle with greater precision and repeatability than using an actual tablespoon

It’s only when measuring half teaspoon stuff where I’ll either just use a teaspoon or pull out precision scales—it all depends how important it is to be accurate with an ingredient.

Is density not a concern?

Yes, which is precisely why I eschew cups and spoons for grams. There are standard conversions for most common ingredients, I’ll tend to use those for ingredients with the potential for high variation in density, like plain flour.

Obviously, the main concern is with repeatability in baking. But for me the biggest benefit is being able to pour all ingredients directly into your bowl (sitting on scales) without dirtying up a pile of measuring cups and spoons.

To provide the correlate to @simondotau’s answer: in cooking, density hardly ever matters. All recipes should actually be solely in units of weight, never in units of volume. Professional chefs, and especially professional bakers, work solely in weights.

Liquid measures by volume are mostly ok, since liquids vary hardly at all in density (for a given liquid).

Solid measures by volume are a joke. It’s easy to be off by 10% or more, depending on how fluffy or packed down your ingredient is. When you’re baking a loaf of bread, this is the difference between a soggy mass and a dry pile of crumbs.

I have a 0.1g precision scale from AWS which ran me about $25 dollars, and it has been indispensable both for the small ingredients and also for weighing stuff like frozen berries, where the gaps can make it hard to determine how much you actually have.

AWS or Amazon?

"American Weigh Scales" is the manufacturer. It has nothing to do with Amazon Web Services.