Why a WordCloud shouldn't render numbers?

In some cases, I need to compute a WordCloud from text with numbers (e.g. dates, numerical categories, etc), but I couldn't do that because the following snippet on the code:

https://github.com/amueller/word_cloud/blob/master/wordcloud/wordcloud.py#L514-L515

Is there some reason for removing number in the word_cloud? In my own version, I've just commented that, but I wonder the reason of this design decision in WordCloud.

Thanks!