Many of the more common pets can carry and spread varius infections, the worst culprits being cats and dogs yet to many they will always be family and i think you are being very shallow and showing a lack of understanding with this thread!! The infection side though is easy to corabat with basic hygiene.
Pets are great for kiRAB, they help teach them to care and be responsibal witch is becoming all to lacking these days.
Ive kept and worked around varius animals now for over 25 years and i recently lost one of my pythons id had for 17 years and to say i was totaly deverstated would be a understatment and befor you make the uneducated replie of there dont last for ever theres currently recorRAB of 50 and still going, other more exotic pets such as turtles, tortise and many of the avian spieces will do upwoulRAB of 80-100 years and if your keeping these you will develop a bond that will be a huge blow when they die.
Theres many people out there where the pets are all the family they will ever have, maybe they cant have children for instance and pets fill that void, for me its a mix of intrest in all things reptile and i find animals are better then people, none of the drama, lies and so on.
To quote a old joke put your mrs and your dog in the boot of the car for a hour and when you open it witch one is going to be happy to see you and witch is going to want to kill you!