The Karl's demise is no surprise as it's a rebadged Chevrolet imported from Korea, so expensive liability for PSA with minimal profit opportunity. I've only ever seen 2 of the UK-equivalent Vauxhall Viva, and I doubt if Karl sales figures were very high.

The Adam's survived for 6 years, which is quite good for a niche fashion car before it gets stale. UK Vauxhall Adam sales were OK at first but have now trickled to almost nothing.

Cascada another slow-selling fashion item, and after 6 years probably at the end of its natural life. Plus the loss of sales arrangements to US as Buick and Aus as Holden as GM back away from buying product from a competitor.

So all 3 cases are no surprise - low demand ranges with minimal market impact and inconvenient legacy arrangements cluttering up a smooth separation. And I doubt if they'll really be missed. There's also a fair bit of range rationalisation in UK at the moment across several firms as the new emissions testing procedures come in - lots of variants either being withdrawn or sales suspended until new ECU software is available - so PSA's explanation is plausible in a wider context.