E-jets and most business jets have tail mounted engines. the reason is mission. tail mounted engines let you have short landing gear and less chance of FOD damage on crappy airstrips. this lets you load pax and cargo with out needing extra equipment. even with under wing engines if you look at the 737 vs A320. the original 737 used turbo jets so they could keep the gear as short as possible when they change it to the CFM's they had relocate the some of the pumps and you ended up with the hamster pouch nacelles to keep the low gear. Airbus when they built the A320 years later airport infrastructure had improved a ton so they just keep the gear taller.