It's "ridiculous" that they don't provide a shower after your economy flight to Singapore? I don't believe showers are a guaranteed minimum benefit of star alliance lounges. Why should SQ go out of it's way to provide extra cost benefits to customers who are not their own premium pax?
How would you advise them to justify it?
I would expect a Business Class lounge to have a shower, it is a benefit that is not guaranteed but an expected facility in a Business Class lounge.
Gold Card holders are regognised through the alliance as premium passengers because of their levels of flying.
So yes, it is ridiculous SQ does not allow Gold Card holders into their business class lounge in Singapore and provides a mediocre lounge that does not have shower facilities.
Globalist