Why database file logs are huge?
Here's a simple analogy as to why transaction logs vs simple backups are vastly different sizes.

Imagine you have the number 10. Each day for the next week you add 1 to it. This gives you the number 17 after a week. 

If you're recording every single transaction in a complex logging scenario you're essentially storing:

10+1+1+1+1+1+1+1


Although in this case each +1 is actually dozens of lines of code!

Wouldn't it be easier just to store the result (17). Now obviously this is less flexible and won't allow you to roll-back cleverly if things go wrong - but that's the fundamental trade-off here!