Probably the only valid reason for using
set enable_seqscan=false
is when you're writing queries and want to quickly see what the query plan would actually be were there large amounts of data in the table(s).
{. Bodie, {. Kane, and {. Marcus. McGraw-Hill/Irwin series in finance, insurance, and real estate McGraw-Hill, Boston, Mass. u.a., 7. ed., (internat. ed.) edition, (2008)