Yep, there are enough services that drop into maintenance mode multiple time a week. Although outside local business hours, one of my banks is in maintenance mode every night (not sure if they do backups or if it's just down and has maintenance mode as 500 screen or what is going on) and the api (psd2 ) does not work then either. Well over 4 days a year I would say and literally no one cares: people are sleeping. So sure it depends on the service but 99% or less does not matter if no one is using it anyway. That said; it is quite bad in this day and age and I really wonder what it is they are 'maintaining'.
This is specific to the domain of cryptocurrencies and blockchains where you are dealing with decentralized networks that slash funds if you are offline for a period of time. It's a different ball game to endpoints you can let fall over and restart from time to time.
