Snow melts in situations which would seem strange to say the least. 

Quick Summary:

Snow layers melt too often due to condition checks that are not present or in line or parity with what the Java Edition has. Cripples some aspects of building, is somewhat confusing. Snow shouldn't go poof just because air is considered dry. Elementary example is Antarctica, cold and dry, and yet still allows snow to exist.

(mcbe screenshots are both in the end, java has optifine text at top of image)

Three Points

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Parity: 

Java edition snow layer checks for light level to see if it will melt while MCBE checks light level, but then biome, and then ignores any attempt at preventive measures such as removing light sources and denying sky access.

Quality of Life:

It would be so great to be able to use snow layers as a reliable utility regardless of what the world seed wants; more freedom for users. Whether that be for decoration, detailing or terraforming, it would still be an improvement for the better.

Realism:

Minecraft is block game. So it doesn't have to accurately detail every aspect of the world it is recreating for us. But, snow shouldn't disappear in say for example the end dimension, where there is no sky light at all, and yet it just goes like that. No light + snow = snow shouldn't spontaneously sublimate away. As for the "Dryness" of the biome, yes, diffusion of the water might work, so it make sense that in a desert with the presence of light, the snow would melt. This should come into play though it still melts if placed underground, protected from any light sources, just because the chunk properties said so. Additionally, I believe there was a "Cold Desert" biome many years ago, though unimplemented, it is still some precedent for some of the ideas supplementing modern day MCBE. Then again, this is block game. But in the end, its net benefit is still worth it.