Which companies in which countries? I'm in Germany and I have never ever seen or (from friends and acquaintances) heard of vacations not taken due to pressure from the employer. It's about as common as an employer arbitrarily deciding to transfer less than the agreed amount of salary at the end of the month - maybe some very dubious employers have done it at some point, but it's not something to worry about.

What is fairly common is employers reminding employees to take their vacation days before they expire. Vacation days from year n expire in April or so of year n+1. That is intended to prevent postponing vacations to never (maybe until switching jobs).