Why many expert players just disconnect on the last round in Hearthstone?

Solution 1:

It seems it must be a causality. Disconnecting from a match permanently counts the same as a concede, so there is no gameplay or statistical advantage to do so, however:

• They may be quitting entirely from playing the game, and instead of quitting out from the main-menu, just close the game straightup.
• It may be quicker to quit out of the game and reboot it instead of waiting through the conceding explosion animation, the XP gain animation, the rank win/loss animation, and the fade-in to the main menu. Especially if they're running on an SSD (Laymans: A type of Hard-drive which means data loads faster) or a high-end rig, it'll certainly be quicker.
• It's possible they're incredibly mad and just do it out of rage

Solution 2:

If you only play a single game of Hearthstone at a time, or you are playing your last game for a while, it is faster to exit the program rather than conceding. Personally, I play on my phone and almost always it's one single match. I can't leave Hearthstone running in the background or else it uses too much power, so I have to force close the app immediately after I'm done. Since I'm going to do that anyway, when I want to concede the match, I just close the app. To my opponent, it looks like I disconnected.