In fact, until the invention of train timetables, people didn’t bother with time zones. When passengers with watches stepped off the trains in Bristol after a trip from London, they found that the local clocks were “wrong”. Of course they weren’t, they were just in local mean solar time while the clock was still in central London time.
Train operators have found it more convenient to have a standard time, however – if someone has to change tracks for a train to turn in one direction after an earlier one has come through the other, timing is easier when they have a clock synchronized with the clocks on both trains and those in the stations through which they come.
That is why we invented time zones in the 19th century so that trains could run on time – or not, but at least whether this is the case or not is precisely defined.
This resulted in each country having a zone, some of which are defined by the mean solar time of a particular observatory, others by offsets from one or the other. Holland’s zone was 19 minutes, 32 and a few seconds ahead of GMT.
In due course, as international travel and communication became more common and the differences between zones were easy to manage, over time countries tended to set their zones in terms of GMT. Some complications eventually led to international efforts to define more precise standards that meet different requirements, including UTC as a replacement for GMT (which is still used as if it were an alias for UTC).
Over time, of course, different jurisdictions have changed the offset from UTC they want to use, so their time zones will have “transitions” that result from these changes. These either repeat a time interval (only in the description of the zone, of course) or skip one and complicate the life of this humble software developer who maintains software that correctly takes these transitions into account and has to get the necessary information somewhere.
However, summer time is sold to make the most of daylight – I can imagine that for some people, whose working hours are inflexible, it is really a kindness and forces them to get up painfully early every day. However, the fact that there are tropical zones that take advantage of it amazes me.