Ik this is a rhetorical funny question but the reason why is so endearing to me. Basically astronomers way back when discovered 7 "planets" in the solar system (that they knew of) and 7 became a really sacred number. These "planets" were named after the gods of the time +

So greek and roman gods were all the rage back then so the "planets" (really just astronomical bodies) were named Mercury, Venus, Mars, Jupiter, Saturn, Sun and Moon [the etymology of the words sun and moon are a bit harder to pin to God Stuff but its there] +

Now, since this number 7 started to get lots of traction, superstitions began forming around them so when it was time to group days into weeks they decided to have seven days of the week named loosely after each "planet" (they reached for some of them to be certain) +

Saturday- saturn's day; Sunday- sun's day; Monday- moon's day; Tuesday- Tīw's Day (old Germanic god of war to coincide w mars); Wednesday- Wōdnesdæg- Woden/Odin's day (supreme god coinciding with mercury); Thursday- Thor's day (germanic god of thunder coinciding w Jupiter)+

Friday- Frigga/Freya's day (wife of Odin, goddess of love to coincide with Venus) +

Long story short, wednesday is spelled like that bc of it's original name amd pronunciation but also bc of Mercury