Also, narrow/wide chain rings, clutch derailleurs and a far greater range of available gearing options has advanced the entire drivetrain compared to 5, 10 years ago...and lets not forget all the advances in disc brake technology over the years.
Not having to choose between 1-2 on the front and then the back gears simplifies things greatly. In addition you also save some weight, it's a much simpler mechanic with less maintenance and with a newer SRAM Type2 or Shimano Shadow+ Clutch derailleur and a narrow-wide front ring you pretty much can't drop a chain, which is great. The only exception would be if you ride incredibly rough terrain where you bounce a lot, but a very simple chainguide fixes that problem.