As a web developer myself I find that I need to explain this to you a bit further, everything that you upload to the internet will always be compressed on any site unless it's a self storage site like google drive or onedrive etc. The reason for this initially was to let service providers save on storage, but now with storage being so cheap it doesn't really matter. The new reason for compression is website loading speed. If everyone had a 25MB youtube banner, can you imagine how long that would take to load whenever someone on a slower wifi connection went to that channel? When you download a 25MB program installer, it probably doesn't download instantly, it may only take a second or so, but if you added that time to simply loading a webpage than you certainly would notice it. Not to mention if people had to cache these images on their computers they would run out of cache space really fast. Catch my drift?