Question

why is standard time considered necessary?

Answer 1

Here is your answer :-

As the local TIMe differs by 4 minutes at every longitude, it would create a lot of confusion regarding time for any country as a whole which may stretch across several longitudes. Therefore each country selects a central meridian and the local time of this meridian is the standard time of that country.

Answer 2

we calculate any places local time by comparing on calculating the distance of latitude between that place and zero degree longitude place .

applying this theory country has several local time in itsaverage time .

this time difference in a same country creates difficulties and confusion.

that's why a standard time on average time is used as the ideal time of that country to avoid such time difference in a same country or region.

hope it helps you