if only 144,000 people will attain salvation

according to jehovah's witnesses, whyy would they dress in suits, subject themselves to the heat on bikes, and jeopardize their ownnn chances at salvation..going door to door? while i think it is silly, there is a part of me that has mad respect for ANYONE who can plaster a smile on their face in those conditions!! imagine believing something So Hard that you would brave the texas heat!!!