Explain why we depreciate assets over their useful lives instead of just expensing them in the year they are acquired?

We depreciate assets over their useful lives instead of just expending them in the year they were acquired because let's say, when we exhaust a 5 year asset in a year, the 1st year is understated because the whole expense of the asset has been fully utilized in just 1 year, while the remaining 4 years are overstated,