LeBlanc's got $60 million in the bank, so he doesn't need to do this gig. It's a chance to indulge in a hobby, and get paid even more money.
You could argue that the money would be better spent on a motoring journalist, but cars are now domestic appliances. They're all reliable, all do the job. There's just various status grades. Reporting on the cars isn't very interesting in itself.
I've recently watched the official PBP DVD, and 'Der Brevet'. They don't bother much with the bikes, the people are more interesting. They also use some of the filming conventions that Top Gear has pioneered. It would need a celebrity to hold the attention of Joe Public, probably that Guy Martin bloke.