The derailleur system fitted on the vast majority of bicycles to be seen in bike shops and bike web sites in this country is a disaster for anyone who just wants a bike to get a few miles to and from the shops or work, and has no desire to become a part time cycle mechanic..
Back in the days when hub gears were limited to three, or at a push, four ratios, derailleurs made good sense for the sporting or touring cyclist who needed a wide spread of ratios. They still make sense to the cyclist who needs the ratio spread
at an affordable price, because a budget derailleur set up is miles cheaper than a precision-engineered internal hub that can offer the same range of gears.
What I actually see as pointless though, are the really expensive derailleurs, because at that price level, you might as well go for a Rolls-Royce quality internal hub gear offering multiple ratios and save yourself all the maintenance and risk of impact damage knocking it out of kilter. However, the cycle industry makes a lot of money selling replacement cassettes, chains, and rear mechs to weekend warriors, whereas they would not make so much selling them a new hub gear once every 20 years!
No-one is forcing us to use derailleurs though, I have more than one 3-speed roadster fitted with Sturmey AW hub gears that are perfectly fit for purpose when used for local utility cycling. For just knocking around on flattish terrain for trips of 5 miles or less, they are my preferred option. However, even a six-speed derailleur beats an AW 3-speed hands down when I need to get up a hill or battle against a headwind.