For drinks like gin and tonics or vodkas with soft drinks, the proportion of liquor, mixer, and ice is carefully calculated for the glass in which it is served, usually a highball glass.
Liam Hirt, founder of Circumstance Distillery in Bristol, also advises against ordering drinks without ice, arguing that this could result in a lower quality drink.
Hirt notes that good quality ice keeps the drink cold and preserves the carbon dioxide for longer, which translates into a more effervescent drink.
Removing the ice could mean more mixer, diminishing the taste of the liquor.