"Real" streamer vs. Bluetooth adapter--what's the advantage?

Hi folks. Please explain this to me in simple terms.

I’m currently streaming from a Galaxy 8 phone, Idagio and Amazon HD, to Audioengine B1 adapter connected by digital cable to a Hegel Rost integrated.

Suppose I got a ‘real’ streamer—Bluos or Cambridge or Marantz. Since I would be using a phone app to tell the streamer what to play, why would the sound quality improve? I’d still use the DAC in the amp, since I reckon that will be better than the one in a $1k or less streamer.

I’m pretty certain I’m missing something, but like the entanglement of sub-atomic particles, I just can’t get my head around it.

Any insight gratefully accepted.

Ca38d923 f90a 4e54 8fa4 f2aaac672eaarsgottlieb
I just got a Bluesound Node 2i as it has TIDAL select so I can use my Android as the controller through the cloud to the Node 2i.... I'll be using WiFi and from all that I researched and read users posts, there are no sonic advantages to an Ethernet connection vs. WiFi.
Bluetooth is a compressed format so sound quality would be better if you are feeding your DAC directly from a streamer.  Apple Air Play is uses your WiFi network and is not compressed.  I don't know if it is as good as direct streaming but it is much better than Bluetooth.  One of the advantages of Air Play is that some streaming services (e.g. Primephonic, which has an enormous classical catalog) use only Air Play or Bluetooth.
COY21's first post and Sfar's posts nail it.
Not all, but many other posts contain incorrect assumptions.
The Node 2i does all the streaming directly from the source via ethernet or wifi.
Your phone only serves as a full featured remote.
No, wifi and ethernet are not equal, but high quality wifi gear and a strong signal can be good.
No conversion to and from Bluetooth.
My phone and bluetooth receiver both support Aptx....it's good but it's still Bluetooth and not even close to what a hi res source can provide.

I'd wager that deleting the phone out of the formula will be a step up, although I still run a 'shop system' with the cell as the source.

I run Spotify on the main audio puter direct from the router sans the cell and I can't find anything to complain about....*S*   
I can recommend the Audiolab 6000n streamer, belting price of kit for the outlay, plays just about every source going.