That's just a joke
I'm sure there are factors that most mobile phone manufactures consider such as slimness and making the phone more rigid / part of the design language /reduce dust ingestion / manufacturing processes / Safety aspects etc. when they make a decision to have a built in battery - the reason as to why we are seeing more and more brands - HTC / Samsung doing so.. I would like to know too ..
But for the layman or average consumer like you and me, most phones with built in batteries are hard for us to replace..
You may need a heatpad / dryer to warm up the glue etc. Citing an example ifixit recently gave the HTC M9 a 2/10 rating for repairability
One probably does have to go to a service ctr to replace the battery if the need arises and I don't think it would be cheap in my opinion.
Removable battery wise - which the Note 4 has... you can buy different types of batteries from other makes such as Zerolemon 10000mah for the Note 4 etc etc etc. - so the phone technically can last for a long time..
But then again having removable batteries brings about an issue of safety - cause batteries may not be certified for the phone / fake batteries from aboard etc.
So there are pros and cons to removable batteries vs non removable.
I personally am on the side of removable batteries cause I can swap it out if I have two or more and I feel that devices with removable batteries can last longer