Roku ultra streaming versus Apple 4K TV

If you look at stock parts, it has been discussed that the "stock" AppleTV is probably the best audio quality when compared to "stock" Roku.  I cannot really say for sure because I have not done a side-by-side comparison.

When you upgrade the Roku Ultra with a linear power supply, that is when the Roku becomes significantly better than AppleTV or any other streamer.

So why aren’t there any designed Products to better play audio coming from a streaming source???

Roku is a mass produced product that is marketed to the large consumer market.  (same with AppleTV and Amazon Fire TV).  Their business is keeping up with all the software changes for the large number of streaming services available.  Since they are a mass market product, the target audience will not spend more than around $100 for a streaming unit.  It's a business decision.  They could make a better product with a better power supply, but not enough people would buy it to give them the expected "return on investment".

There are some newer devices such as Zidoo Z10 that use a newer version of Android OS.  You can tweak the device with a special firmware to allow download of certain streaming software from the GooglePlay collection (such as Netflix or Amazon Prime), but the user interface is horrible because it is designed for phone/tablets which require touchscreens.