Jono, there are straight retrieves and then there are straight retrieves. Most novice lure anglers simply whack a lure out as far as possible and then wind the lure back at a constant speed, that very rarely changes between casts. Certainly, that can and often does work but a straight retrieve doesn't have to be quite so mechanical.
Let's take a spinner as an example. It's the simplest of all the straight retrieve lures to operate. You can just cast them out and wind them back and they do cover a lot of water but I think they can be made to do a lot more than just hum along, singing the same old tune. Varying the speed throughout the retrieve is fairly obvious but you can let them sink and then rip them up again, sink and draw style. Another trick is letting them stall without the blade stopping. If you give the spinner a good fast crank and then sweep the rod back and then pick up your line while maintaining a tight line, as you bring the rod back to the forward position, you can make the spinner 'hang' momentarily on the spot with the blade still turning. I hope I described that action correctly. Sweeping the rod from left to right to left repeatedly will make the spinner change direction more noticeably as the lure approaches. There are more techniques that can be employed but the main idea is to mix these retrieve styles up as much as possible within a single cast. All of these styles are still basically straight retrieves but it demonstrates that it doesn't need to be monotonous. Apply these ideas to any straight retrieve lures and they'll all come to life.
It's also worth noting that some lures that are thought of as purely 'worked' lures, such as jerkbaits, often benefit from the opposite approach. Take the Salmo Slider. I mentioned that it is a very easy to learn glidebait. Getting a walk-the-dog type action out of it is fairly simple to master but it works very well if you simply throw it out and wind it straight back it. It's a very realistic, photographic lure so it passes itself of as a real fish fairly easily. Wound straight back in, it wobbles ever so gently and just sometimes, that is all it takes to warrant a hit. Erratic retrieves are, as Derek says, more productive for the most part. That is without question but just sometimes, when all else fails, remember that novices catch fish when the experts are blanking so casting and winding should never be discounted.
