Ethylbenzene is generally prepared by acetylation of benzene followed by reduction and not by the direct alkylation of benzene. Think of a possible reason.

Explanation

Preparation of ethyl benzene from acylation of benzene and reduction can be shown as

The direct alkylation can not be performed because there is polysubstituion product is formed. Due to disadvantage of polysubstituion that Friedel-Craft's alkylation reaction is not used for preparation of alkylbenzenes. Instead of Friedel-Craft's acylation is used.