I've had a work phone since probably 2005? Man, I've seen some evolution in the smartphone marked during that time!
For me it's more that the company expects me to travel, and to visit customers, and it's simply impossible to function without a smartphone in the modern era in that environment.
I like that it gives me a lot more flexibility. I'm about to go take my lunch hour at the driving range (which might extend a little beyond an "hour" lol) but I know that if there's something critical I'll know about it. My job isn't really "9 to 5" in the sense that I don't have flexibility.
The downside is that when something comes up that requires after-hours work, I may have to deal with it. Over Thanksgiving weekend we had a critical situation at a customer and while I wasn't working hours upon hours every day, I was responding to phone calls and emails for that issue every single day of the weekend. I had to call my VP and update him on status between the 9th green and 10th tee on Sunday morning that day...
I do my best to balance it. If something comes in after hours but isn't urgent, it waits until the morning. With WFH and a dog that wakes me up early for walks, I start my work day pretty early in the morning anyway, so if I don't get to your email until 7:40 AM PT, you're just going to have to deal with it.