Companies nowadays, value employees choice when it comes to their work schedule. Some of them prefers to be flexible when it comes to their shifts while others prefer to have it fixed. The choice of this depends mostly on the employees lifestyle and thus benefits each worker differently.
Firstly, for people who have families, especially ones with young kids, they might prefer to have a set schedule so they can arrange day care or babysitters. Also, having this set working days is also beneficial as one can easily arrange vacation days unlike to those who do not have a fixed schedule as they do not know that days they are at work until a few weeks before the rota comes out. Although, they may request vacation days but then again it depends on if the chosen days would be approved. This arrangement can also be helpful to those who have a part-time job as they can easily go to their second one right after the first or vice-versa. Moreover, not all the type of work benefits from this kind of schedule.
However, while having flexibility at work also have a ton of benefits, this may not be suitable for people who have families as their schedule changes all the time. Although, I find this suitable for myself as I can arrange to go to work on my pace and I can choose to go to work on the days opposite my husband and thus can save us money because we do not have to enrol our baby in the day care.
In conclusion, while both have their own benefits in each their own way, it still varies on how it suits the employees themselves.