The Samsung Galaxy J7 Max have non-removable battery. For me having a replaceable battery is certainly an advantage. Having an option to just pop out a battery to replace the emptied one is a great plus. I know that battery packs are cheap nowadays and many use them to charge up their phone on the go. The thing is that you need to connect the phone with a cable to charge the battery. It works like a mobile electric outlet. There are battery covers but those are are bulky.
When I am out for some video shooting, I always bring two more batteries with me. I just charge the batteries at night and when I know that I'll be using the device for games or taking pictures and videos, I bring them with me. I don't need to worry about the battery dieng on me in the middle of the day. Right now I am in Portugal and I take lots of photos each and use the GPS quite a lot. This really depletes the battery really fast, especially the GPS for Google Maps and other apps that use the GPS.
For travelers, having a removable battery is a great advantage. As you can see, I am not a big fan of phones with non-removable batteries, and the Samsung Galaxy J7 Max is no exception.