That’s the main reason. Even if it’s only a few minutes, I’d rather rather minimize it if it’s not critical.
On that note, I probably should be holding off on using a beta plugin for the potential for downtime alone. 
I’ve loosely followed some of the discussions on ‘zero downtime’ upgrades. Perhaps it’s just rose-colored glasses looking back on recent history, but it feels like I’ve been able to use /admin/upgrade for most updates over the past year, so I’ve been focused on more critical projects for the time being and lost interest in the zero downtime approach.
When I migrated to a bigger host back in January, it was ‘zero downtime’ in that users could continue to access content on the site, but there was a brief period where things were read-only as we transitioned. I suppose I could use that approach for a major data container upgrade if I really wanted to minimize downtime during the next big data upgrade.
PS. I’ve read a ton of your posts in the community here over the years. Thanks for all your efforts in supporting the community! 