No it's not a must but it's very helpful. Chips can be read by most readers which AC, vets, and shelters have on hand. It also carries all of your information on it, collars and tags can be lost but a chip will stay with the dog for it's life.
The only downsides to chips is always making sure your information is updated at all times. But that's usually just a quick email to the company which takes maybe 30 seconds, nothing big
Jasmine - Female Miniature Poodle - born Aug 15, 2010
Loker Delgado Von Stalworth - Male GSD - born Jan 26, 2012
Koda & Zazu - 5 year old male cats
Alex - Male Cocker Spaniel (rescue) - RIP Cuddlebug 2007-2010