They often do. So while you can buy "cask strength" whiskies at 50-ish percent (iirc last SMWS one I had was ~60% which was ... a little much), scotch is usually bottled at 40-44% (40% is the legal minimum).

As to why they don't always bottle it at the mixed strength - perhaps it's because these higher-proofed whiskies are more for enthusiasts who will explore the whisky at different levels to find what they enjoy best.

One other reason why is that tannins have longer shelf lives than many of the component flavors they lock together. Splashing it at the time of consumption is "fresher" than trying to bottle it that way.

They do. Though what is the preferred mixed strength is highly subjective and so many whisky drinkers will by “cask strength”, which is >60% ABV vs the 40% you’ll find in the ones people will often put with mixers. And then water it down to the strength they prefer. The act of adding the water itself will provide a different experience given the way it interacts with the volatile compounds as it’s mixing. So a whisky you water down yourself to 40% (not that you’re accurately measuring that at the time) will have a different nose and palette to one that came pre-bottled at 40%. Some people have a preference for cask strength mostly for the snobbery of it. Others prefer the higher ABV if you’re drinking it neat (or near neat) and the fact it’s more true to what came out the cask (I had a >80% rum from the SMWS once that was incredible). I preferred it mostly because it felt like better value; you tweak the water levels and it’s like you’ve got a dozen or more different whiskies to experiences in the one bottle. Maybe even the one glass if you’re adding incrementally as you drink.

Adding ice is more commonly frowned upon for all of the opposite reasons to the above. The cold shuts down the volatile compounds, and it dilutes the whisky (and thus changes it) in a way you have very little control over. That said, on a hot night or even just in front of a roaring fire there can be something exciting about that too.

The only wrong thing would be to say “true scotch drinkers don’t do X”. There’s no more appropriate place to invoke the No True Scotsman fallacy.

Cask strength refers to the strength that it's put in the cask, and such whiskey is unaged. It looks like a clear spirit. The alcohol evaporates over time (this I believe is called the Angel's share) and so after aging it's closer to 40-50% abv

"Cask strength" refers to whiskeys that have been aged in the cask, angel's share and all. It means that the manufacturer didn't dilute the product any further before bottling.

This is incorrect, it’s the strength it comes out the cask. How else would you explain the the vast array of single malt whiskies that are cask strength and aged anything from 10 to 30 years (e.g., https://www.connosr.com/glenmorangie-cask-strength-10-year-o...).

Bottled at 40% is because they watered it down.

Could there be two definitions I wonder? I might just be wrong, but I'm basing what I wrote above on a clear whiskey that I tried at a whiskey tasting, that was referred to as cask strength, with the explanation I gave above.

No. A very quick google can confirm for you the definition of cask strength.

It's not legal to call it whisky below 40% abv, and also it allows you to add water to get your desired mixture.

Personally I like having a few sips neat, add a drop of water, another sip, a little more water, etc. You get to enjoy it at a variety of strengths instead of just the pre-mixed weaker strength.