Why do mobiles need many categories of LTE cat?

Why do mobiles need many categories of LTE cat?

LTE Cat: the meaning of the abbreviation and what the speed category affects. What is frequency aggregation. Which LTE Bands are supported by Russian mobile operators. Basic modes of LTE. But within this standard, there are several substandards that differ in speed, frequency and other communication parameters and are marked with the designation LTE Cat. 4G connection. 3G has been replaced by 4G.