Most people by default do take a fair number of breaks, naturally through the office/coworker/commute context. May not seem like much until you don't have that. 8 hours in the office is not 8 hours of distraction free in-zone work.

Solo dev is somewhat unique in that you have none of that.

Rolling out of bed, having a cup of coffee, working 15 hours straight without leaving the chair once is legit something that happens if you don't watch out. If for no other reason than kidney health, that's no good.