Why is it more practical to prepare karyotypes (the number and visual appearance of the chromosomes in the cell nuclei of an organism) by looking at somatic diploid cells rather than haploid gametes

Answers.

this is because the the set of diploid chromosomes in the somatic cells  must be  be examined/observed  to determine the chromosomes count of an organism.

In order to carry out karyotypes, the two sets of  or complete set  (2n) of chromosomes in the diploid cells  of an individual need to be examined under microscope, so that certain features for comparison between each chromosomes of the diploid pair, e.g length,  position of centromere on one  compare to another, the banding pattern etc. needed for accurate comparison can be obtained. thus  with this any  abnormalities e.g  deletion, addition, or duplication in chromosomes number can be determined

Naturally under normal conditions, autosomal  chromosomes ( all chromosomes in the body of living organisms  excluding  the sex chromosomes) exist in pairs in diploid organisms, thus this is a good pattern for comparison.

A haploid gametes only contain just one chromosome, thus there is no standard for comparison  to observe and obtain   desired  features for karyotyping with haploid gametes.

we would need to see the picture to answer it