Block Confirmation Speed - Bitcoin vs Litecoin vs Potcoin
Short answer, bitcoin was first. altcoins that came after thought that took too long and shortened it. Litecoin was one of the first ones that came after bitcoin and they made it 1/4 of the 10 minutes in bitcoin.

Long answer, there's a balance that each coin tries to make between block propagation and speed of confirmation. Satoshi was pretty conservative in choosing 10 minutes as there weren't any other digital currencies like bitcoin. Other coins have since tried shorter times, some as short as 10 seconds and have found that it works fine. There have been suggestions by former core devs that a hard fork could be executed in the future to shorten the confirmation time to 2.5 minutes or less for bitcoin.