It can certainly be a design goal if you want it to be. Sometimes truly dynamic programming is what you want and need. I, personally, wouldn't want to write any code like that because I mostly write software for other people that runs while they aren't looking, not for myself that runs when I execute it. Lisps are popular in academic settings where the program behavior is the topic of interest and maximum flexibility is a tool to accelerate progress. These types of scenarios usually have the person who wrote the code directly involved in it's execution, as opposed to service development where you want to be more sure it'll actually work before you deploy it.
Comments
In another word, it (to have runtime macro expansion) is a side effect, a compromise, a wart, rather than a design goal, right?
It can certainly be a design goal if you want it to be. Sometimes truly dynamic programming is what you want and need. I, personally, wouldn't want to write any code like that because I mostly write software for other people that runs while they aren't looking, not for myself that runs when I execute it. Lisps are popular in academic settings where the program behavior is the topic of interest and maximum flexibility is a tool to accelerate progress. These types of scenarios usually have the person who wrote the code directly involved in it's execution, as opposed to service development where you want to be more sure it'll actually work before you deploy it.