Sometimes it's needed to help prevent a service being overwhelmed: our phone calls used to cost 4x more 9am to 1pm than 6pm to 8am because our phone service (government run) had limited available bandwidth. Now that is no longer an issue (largely c/o fibre optics) there is no pricing surcharge for the daytime peak.
In fact on a wholesale level from BT there still are three different time bands for pricing (daytime, off-peak, weekend) and different charges based on whether the call just goes through the local exchange, one regional ('single-tandem') exchange, or two ('double-tandem', which in turn is broken down into short, medium and long distances). Retail phone companies tend to lump them all together into a single rate, though - either an unlimited use bundle, or a simple flat-rate per minute.
For that matter, many of the better ISPs still have some time-based variation in charging: my previous one only charged for usage during the working day, my current one has three tariffs, one of which is much much cheaper outside working hours. (The worse ISPs tend to offer "unlimited" service, and accept that their network is congested and slow at busy times.)