It is unreasonable. It’s just been normalized in certain settings. I’ve been in teams like that, and having to check in while on vacation makes it hard to take your mind off of work. Its one thing if my manager asks for my cell phone in case there’s a true emergency. But having me check my email every weekday? No. Boundaries are healthy.
I’m never again working in an environment like that if I can help it unless the company really makes it worth it, and let’s be frank most small companies can’t afford to do that.
For some people, a vacation is just spending all week at home playing video games. Others will just sped time at a B&B or visit family. For them, checking email is not a big deal.
Other people are way more active and want to go camping, surfing or something else that gets them away from their phone/laptop. For these people, checking email is unreasonable because it interferes with their plans.
The two types of people cannot understand the other side. One of them thinks "Why can't you spare a little time in between checking Facebook and Twitter to check your email?" The other side thinks "Who wastes a perfectly good vacation by spending any time on Facebook and/or Twitter?"
I’m never again working in an environment like that if I can help it unless the company really makes it worth it, and let’s be frank most small companies can’t afford to do that.