It is a small performance improvement, but it can add up in larger apps or apps where the view is rebuilt often for example because of animations.
const reduces the required work for the Garbage Collector.
You can enable some linter rules in
analysis_options.yaml that tell you when you should add
const because it’s not inferred but would be possible like
or that reminds you when you use
const but it is inferred anyway
See also https://www.dartlang.org/guides/language/analysis-options