Tip is not longer a tip. You know, when tip actually ment giving extra money to someone who did a good service for you? It is now expected to just stash extra money for someone that is ment to be doing their job in the first place. Luckily majority of service staff tend to be nice and provide a good service, but dont be thinking you getting a tip if you are having a shit day and barely putting any effort into your job. Promotes wrong behaviour.
Now delivery drivers to my door, I tip when I have coin. Just Eat does not have tip option in the UK. But welcome to 21st century, I don't carry cash.