When the leave policy allows for more days than the legal minimum I see no problem with carrying over a few days. An employee may be perfectly happy to take 4 weeks one year knowing they can carry the extra week and take 6 the following year for a one-off longer holiday, getting married, or even starting a new man shed project
It's not going to affect work life balance...inability to book leave due to staffing levels and being forced to use up leave at unappealing times of the year is no doubt a much bigger work:life/moral killer than ensuring and employee uses/loses their leave allowance within 365 days.
In the company like mine it's difficult getting Christmas leave until the last minute when they decide to relax the thresholds so the carry over also allows us some slack if we use more or less than expected. This year I have 1 day approved, but it's likely they will offer more on Christmas eve.