grammaticality - Use of seemingly wrong grammar in the poem(s)

I read the poem 'A Roadside Stand' by Robert Frost, and I have accumulated a few questions through the poem. So, I will be posting some questions from the same poem, if you can, then please answer my other questions as well. Thanks to all :)

Have a look at the picture of the text I have added.
I have highlighted two things in the poem, which are concerned to this post.

First, the use of 'rest' instead of 'rested' seems wrong to me. Is poet's use of 'rest' really wrong grammatically? If it is not, then what difference it will make if 'rested' was used instead of 'rest'?

Second, the use of 'why keep their money' where I feel like 'why not keep their money' should be there. Is poet's sentence correct or incorrect grammatically in this case? If it is correct then what difference it will make if 'why not keep their money' was used?

I have seen this kind of grammar being used in several poems, is it a kind of a feature of poems in general?

(I'm not a native speaker, probably that's why I have these questions in my mind. I will be really happy if you could help me reach the answers to my questions.) Thanks again to all :)

Answer

poetic licence oxford english

noun

The freedom to depart from the facts of a matter or from the
conventional rules of language when speaking or writing in order to
create an effect.
‘he used a little poetic licence to embroider a good tale’

as @BillJ said poets exercise exceptions!