I did, I had a 2.5 year old who had been going to nursery 2 x per week whilst I worked (other days looked after by family/OH), when I had DC number 2
We still sent DC to nursery once I was on mat leave, firstly to ensure normality and familiarity, the upheaval of a new baby on a toddler is immense and often doesn't show within the first few weeks.
Secondly, we needed to maintain the space, I knew I had to return to work after mat leave and if I had let the space go, I would have had to look for 2 x nursery spaces within the same setting, as opposed to just the baby space, which was easy to sort as conversations happened with nursery at drop off/pick up....also we already had the relationship with the nursery.
Lastly, having a few days without the toddler, can allow you uninterrupted time with the baby and not to feel guilty that the toddler is having to wait an extra minute for attention.
It's nothing to do with not having them both at the same time, that just happens, but if you are lucky enough to have childcare and be able to fund it, I would continue using it.