Why is public transportation within the city so slow?

So I commute to college everyday and my route is very nice I have to say, it goes straight from my house directly to college, and 70% of the commute is in a straight line. YET, it takes generally 40 minutes – 1 hour+ when by car, even when freeways are jam packed is maximum 25 minutes.

Also the buses are seldom on schedule to what the Metro SMS tracker says.

So is there a reason for this? Is this generally how public transport is or is this just a Metro thing? Because I have a super convenient bus commute – I can only imagine how hard it is for people living elsewhere where they got to take transfers, etc.

Can’t afford a car because insurance screws you raw and I like to drive on the roads legally.