Given the end results of the two types of division, why is it necessary for homologs to pair during meiosis and not desirable for them to pair during mitosis?

Meiosis is a reduction division. The formation of haploid chromosomes at the end of meiosis, from formation of bivalent, at late pro phase 1, and eventual easy alignments on spindles for separation at meta phase of the two stages at the end of meiosis 1 and 2 allow for easy paring and recombination to form new haploid cells at the end of meiosis.

However, mitosis is a multiplication division (2n) the chromosome numbers are double during division; therefore it will evidently mechanically hard for perfect alignments and pairing of the chromosomes that will lead to formation of identical daughter cells of mitosis if homologous chromosomes were paired.

The unparing of chromosomes during meta phase ensures that only centromere division is needed for distribution of similar chromosomes compliments of the parents to the new daughter cells.