Don,
Some drivers may face an insurance surcharge if the ticket shows up on their record. Sure, the $100 fine may not hurt much, but insurance could easily increase by that amount or more for every six months of coverage, and ins. companies typically keep the surcharge in place for 3-5 years. An extra $200/yr for five years adds up, and may make the lawyer worthwhile . . . it's a cost-benefit issue, for sure, though. For some, it would be much cheaper to pay the fine, take driving school, etc. and be done with it. For others, it might be worth it from a dollars and cents perspective to fight the ticket.
Just a thought,
Tort