Every worker as a right for holidays. Yes, especially in Europe this promise by the declaration of human rights is seen as very important, while in the US the amount of holidays is generally quite limited. So in Europe most scientists, as most workers, have the right to something around 25 to 30 holidays per calendar year. Many enjoy it, but when you talk to scientist you often hear some form of guilt when they take it. This post should address the reasons for it and are of course only my own observations.
Scientists were once students and for many subjects the workload during the study time is relatively high. I have explained last time the maths behind the theoretical study hours and e.g. in Germany they add up to roughly 60 h/week (perhaps I will explain the background of it another time). Within this time, students are mostly self-responsible how they plan their days. Yes they got lectures and practicals, but the basic idea is that they learn to organise their work on their own. With a large workload ahead, which always seems larger than that what they can achieve (which makes sense, as everybody has the same requirements, and a lecturer has also to cover those which are some sort of genius), the feeling that you cannot do enough is quite common. For some this leads to procrastination and the feeling of constant failure, which makes it hard to succeed in the studies. Others learn to manage it somehow, but still many have at least the feeling that they do not enough. In the PhD-student time this usually gets even harder as there is even less amount of time preplanned for you.
When you have managed to get you PhD and work as a researcher, you again have to organise your time and usually many work more than their 40 h/week. They also work in part for themselves, as the contract times are limited and to get a next job requires you to deliver excellent results in the previous one. So for many work and life merges to a mix, which do not really know a line between these two worlds. This can be hard for families (anyway, many researcher have to change their location every couple of years), but also it leads to the problem that some researcher feel obligated to their research 24/7/365.
A holiday, even when it is much deserved and needed for the person, is therein a contradiction to the everyday experience, which scientists had for years. Many researcher try to be reachable via email anyways, do not really take a step back from the work and even working holidays (just to write another paper in another environment) are quite common. Of course this can lead to less productivity, problems or even burn outs, but for many this is part of being a scientist. And yes, this is not much different to those people working in business or industry, as nowadays many people feel to be obliged to work whenever they can and in every situation. So when your holidays are ahead, try to enjoy it and when you got another year in which you do not feel the need to get out of your job for a couple of weeks give it a try, it might be beneficial for your work output in future.