I thought ß was being phased out. In fact, I heard that like 10 years ago at school during a German class.
They just sound the same to my hears, so I got around it by memorizing the respective use cases.
OTOH it could also be just spending priorities of updating street signs vs. other things.
I knew nothing about the phasing-out of ß until reading the comments on this article.
In Switzerland, "ss" is standard (Duden says: "In der Schweiz kann das ß generell durch ss ersetzt werden <§ 25 E2>.") I haven't seen "Strasse" on signs in Germany, but there might be regional variation (since street signs are a local-government responsibility)