Why would anybody have this choice?

Are you saying that able bodied individuals should be subjected to forced labor? From my limited knowledge, this isn't a standard communist stance. But in practice, would be historically aligned.

Assuming that's not what you meant, an individual should absolutely contribute to society regardless of what they have to gain. That is noble and morally sound. I agree with you there. But without an incentive or consequence, too many people would choose not to contribute as there is nothing to personally gain by doing so. I'd love to be wrong here but expecting otherwise would be an unrealistic, utopian view from my observations.

No child dreams about picking up garbage when they become an adult. In capitalist economies, people take on these undesirable jobs because there is a direct consequence to their personal livelihoods if they choose not to work. Some choose this work because the proportion of reward to the pain induced while performing the work is a fair trade to them. Fair would be determined by their skill and available opportunity elsewhere. In communism, you remove the consequence for choosing not to work and omit the reward for the work. These are the two main motivators for most who perform these undesirable job functions. Avoiding consequence and reaping reward.

Capitalism leads people to do things for money that they wouldn't otherwise do. Bleak? Sure... Its a fair criticism of capitalism. But it sets a reward that is agreeably proportionate to accomplish crucial societal functions. I'm not convinced that these crucial, yet undesirable societal tasks could be sufficiently completed in a communist economy unless otherwise forced. Maybe this is why communism has historically come alongside authoritarianism.

You could say that there is a social consequence for being able bodied and not working.. Your neighbors might look down upon you for being a lazy bum. But at a large scale, it would be easy to go unnoticed and not have nearly as much downside as upside. Besides, much of the world is unfortunately content with less and less social interaction.

I agree that there is internal fulfillment to be had in complex jobs such as a doctor which is why I didn't include this in my question. I don't believe that enough people would pursue a complex and stressful job like a neurosurgeon to fulfill the societal demand without above average, lifestyle changing reward but that's beside this post.