Environment variable is not always printed correctly - variables

Question

When I write such script in simple Jenkins pipeline:
pipeline {
agent any
stages {
stage('Build') {
steps {
echo "${env.HOMEPATH}"
}
}
}
}
I receive this output:
Started by user USER_1
Replayed #36
[Pipeline] Start of Pipeline
[Pipeline] node
Running on Jenkins in C:\Users\USER_1\AppData\Local\Jenkins\.jenkins\workspace\2nd_pipeline
[Pipeline] {
[Pipeline] stage
[Pipeline] { (Build)
[Pipeline] echo
\Users\USER_1
[Pipeline] }
[Pipeline] // stage
[Pipeline] }
[Pipeline] // node
[Pipeline] End of Pipeline
Finished: SUCCESS
However when I write in pipeline script only this:
echo "${env.HOMEPATH}"
I receive only this:
Started by user USER_1
Replayed #37
[Pipeline] Start of Pipeline
[Pipeline] echo
null
[Pipeline] End of Pipeline
Finished: SUCCESS
My question is why when I write only a single line in pipeline script to print env.HOMEPATH I receive null, but when I use pipeline block the variable is printed correctly? HOMEPATH is a variable defined on my the only one node (master) so it has been also injected to Jenkins environment variables.