Would be cool to have a special event happening for every grindy legal job on the server.
For example during pizzaboy you get to deliver pizza to a party at one of the homes already scripted as a destination which means you can deliver all pizzas remaining on you for $150 each and $25 tip. Of course it'll be a low percentage of this happening but it'd be satisfying to consider yourself having this luck.
For garbage job it could be that one of the locations drops more than 1 trash bag around because the garbage bin is piling overly full of trash, meaning you can pick more up at once so you won't have to drive around much to have your truck fully filled.
For trucker job it could be that the owner of the business is very happy with your fast service and decided to double your payment (Of course only with the scripted ones, not with the manually ordered ones).
Having that extra chance of some luck during your job which otherwise might get repetitive could be a good motivation to keep going.