Basically, because alcohol is no joke. The amount of personal tragedy it produces year by year is staggering [1]. Yet as a society we currently decide it to be worth the costs and shift the responsibility to the individual: "drink responsibly". So when someone tells you "my responsible behavior is to not drink", I find it quite reprehensible for you to answer "I know better, you should drink anyway".

[1] Also speaking from personal experience, unfortunately. Yet it is hard to get a good feeling for how may lives it impacts, because cold statistics [2] don't resonate properly, and many stories occurring in you personal circle are deemed family matters or similar. It's only when you open up with your own problems / problems of people close you, that others open up as well.

[2] Edit to add: https://jamanetwork.com/journals/jamapsychiatry/fullarticle/... - "Prevalence of lifetime and 12-month alcohol abuse was 17.8% and 4.7%; prevalence of lifetime and 12-month alcohol dependence was 12.5% and 3.8%."

Not OP, but:

1) Pressuring (as opposed to discussing, persuading) anybody to do anything they’ve really got their mind set against is usually fairly toxic behaviour, especially if there are likely to be distinct downsides to that behaviour. Edge cases might be acceptable but generally it’s toxic.

2) It’s a widespread problem due to the widespread adoption of drinking and/or binge drinking practices in many societal groups.

(I speak as a drinker, who I have to admit has sometimes wondered “what’s wrong with you?” when someone is strictly teetotal.)

Also not OP, but I can think of a number of reasons:

1. Awareness that alcoholism runs in the family, so better play it safe and not drink

2. Association between alcohol and past trauma e.g. alcoholic abusive parent

3. Past relationship that ended due to ex-partner's alcohol problem

4. Religious conviction

Alcohol has psychological effects and peer pressuring people into experiencing them seems pretty not cool.