But do you sit drinking it all day, or do you slot in with your hosts and their routine somewhat?
I find these things rarely conflict. I can play board games or charades, chat or watch the telly with a lovely cup of tea on the side. I didn't realise this was some sort of spectacular multitasking feat 
I have friends who only ever drink water or weird green slurry stuff, they never mind if I put the kettle on for myself in their houses. I never mind if my guests want to make themselves a hot drink, or install a jug of their weird green slurry in my fridge. It's nice to feel at home in each others' houses.
I will admit I sometimes have a stealthy vape in places where I don't have permission. With a low powered device, PG based and lightly flavoured liquid and a bit of practice in front of a mirror it's perfectly possible to go unnoticed. I once had the pleasure of travelling to a demo with about 12 seasoned vapers in a tube carriage. They were all vaping but unless you were watching at the exact moment they inhaled you'd never know. Nobody else in the carriage even noticed.
If it's someone's house I'm respectful enough to go outside usually but have been known to nip to the loo. The trouble with making vapers go outside is that it doesn't work like smoking. If you're having a fag you light it, then hoover in a massive spike of nicotine in about 5 minutes and don't want any more for a good hour or so. If you're vaping, you go out, have a couple of drags and that's enough but 10-15 minutes later you want another couple of drags. Going out each time is impractical. If you try to vape like you smoke - hoover for a solid 5 mins, you're likely to be sick. As a very wise woman once said, 'smokers binge on nicotine, vapers graze'.
Luckily, most vapers find their dependence on nicotine diminishes considerably after a while so it's not a huge problem but for those who have only recently switched, making them go outside will lead to considerable craving and could mean the difference between success and failure.
My main concern is the massive death toll and health issues caused by smoking. It would be good if people were a bit more understanding and accommodating of people who are trying to prevent that.
It would also be good if vapers could learn to be polite and discreet when necessary. Most do, but unfortunately people don't notice polite discreet vapers, they only notice the ones who are not polite and discreet. Just like they never notice the smoker who takes themself far away from other people before lighting up, or the family with well behaved toddlers in the restaurant, or the people who manage not to smell despite not having a shower every day (I've been on MN too long haven't I? ).