IceKohl When you consider that some areas of the US respect daylight savings time and some don't, computers need some way to represent that. For example, some counties in Indiana in the US doesn't respect daylight savings time. So from a computer perspective, even though indiana is in the Eastern time zone, you'd want a different time zone than Eastern for those Indiana counties, so that computers know the correct way to keep time in those counties.
That's just one example out of countless examples. time zones are very, very, very complicated. If you're interested, check out https://www.zainrizvi.io/blog/falsehoods-programmers-believe-about-time-zones/