My boy can be lazy. Not to that extent, because I don't allow it. I don't even allow the minor "oh I can't really be bothered, I might fall out of canter into a trot for a couple of strides"... I get RIGHT up him and kick his butt.
I don't ride with a whip because for whatever reason they make him bolt, even if I'm not touching him with it. And also, they screw up my hand position. I struggle with piano hands enough as it is and a whip makes the problem worse. I think a whip actually caused the problem.
I do have a pair of spurs that I will put on if he is being a pest about forward, but I don't ride in them full time because now and then he has a day where he's too forward, or when he'll buck and bolt the moment the spur touches him. My spurs are very short and very blunt, and child sized because the adult sized spurs are longer and I wanted the shortest ones I could get.
When asking for forward, you go about it in gradients of pressure. First a very light touch/squeeze, then a firm squeeze if you're ignored. If you ride with a whip, the next step if horsey is STILL ignoring you is to hit them, HARD, just behind your leg. Still being ignored? Hit EVEN HARDER.
Do as little as possible but as much as necessary is my philosophy. Your horse is educated and KNOWS what you're asking for. That means HE WILL DO AS HE IS TOLD and he will do it NOW. If you have to get mean, GET mean. I have been accused of abusing my horse before now because he was ignoring my lighter aids, so I gradually got firmer and firmer until I was being quite harsh. He did as he was told. The next time, he was lighter. And the time after that, he was lighter still. I apply this philosophy to EVERYTHING- groundwork, forward, stopping, turning, walking through water (my horse has been an eventer his whole life, HE KNOWS it won't eat him), you name it.
This is a horse that will back up at liberty from the twitch of a finger, and change direction based on where my body is in relation to his. He will transition from canter to trot, and trot to walk, purely off my seat, and I have gotten upward transitions from walk to canter ALSO purely off seat. But he will try it on, and I have been forced to yank on his mouth to get him to stop before now... and flying kicks are not an uncommon occurrence, even with spurs on! If I let him get away with it, I would have a horse that was ALWAYS heavy off EVERY aid, because he would learn that he can get out of having to do as he is told simply by ignoring the "please?"... but for some reason outsiders don't understand that and they see the really firm aids and think I'm horrible.
I equate it to dealing with children. You ask them nicely and a lot of them will respond really well to that and do as they are asked (or at least they do for me??), but those that don't, sometimes you have to yell.