I'm not sure that's an entirely fair way to frame that. ADHD people can be highly motivated by reward, but being motivated isn't enough to consistently navigate the path from wanting something to getting something. Reward can make you want something more, and even try harder for it, but ADHD means that sometimes no matter how much you want something and how hard you try it just doesn't happen.
N=1 here, but for me, anything that's more than an hour or two in the future rapidly loses any motivating power; any reward that happens after more than a day may as well happen at infinity.
We seem to have a different understanding of the word motivate.
I use it in a very straightforward sense: motivation is the energy to move forward to your goal. It's motive force.
For example, I might understand that I need to file taxes, pay fines, or apply for such-and-such benefit, I might want to do that for the rewards (or lack of bad consequences for filing late), but I just can't motivate myself to do it until it becomes an urgent emergency and everything is on fire.
As in, I can't get myself to move on this task.
>ADHD means that sometimes no matter how much you want something and how hard you try it just doesn't happen.
We fully agree here.
Executive functioning is a better term to use, but people are familiar with motivation more.
Both meanings look like they're valid uses of the term. The "to cause to take action", "to cause someone to behave" and "to incite/actuate/propel" definitions focus on what initiated an action/behavior, while most of the definitions I found focus on just having or providing a reason/incentive/desire/enthusiasm/encouragement for an action which applies even if that action never actually materializes.
to give (someone) a reason for doing something
to be a reason for something
https://www.merriam-webster.com/dictionary/motivate
To provide with an incentive or a reason for doing something; impel:
To cause to be enthusiastic
to give incentive to
to provide with a motive or motives; incite; impel.
https://www.thefreedictionary.com/motivate
To provide someone with an incentive to do something; to encourage; to actuate.
To animate; to propel; to cause to take action.
https://en.wiktionary.org/wiki/motivate
to cause someone to behave in a particular way:
to make someone want to do something well:
https://dictionary.cambridge.org/dictionary/english/motivateWe consciously want the thing, but that isn't enough for executive function to kick in, so "I need to get off the sofa so I can make tasty dinner" results in not having moved two hours later.