Possibly because there are far more people who want to be flight attendants? It's a job that from the outside appears fun and exciting but is often not something people keep going with as a long term career as it's completely incompatible with normal family life, so if you've got a fairly high turnover of staff you're likely to have a lower average wage because they've not been there as long.That's a fair comment, so why are flight attendants only paid an average of £20,476, significantly lower than what would be perceived to be an equivalent role in the rail industry.
IIRC the likes of RyanAir and Easyject have pushed down the average wage for them by quite a bit.
Oddly enough the people that work on the manufacturing line tend not to have a massive input into the design and materials of what they're making, you can put something together perfectly according to specification, but it doesn't improve a poor design that is made out of poor materials (no amount of care and attention a skilled production line worker can lavish will overcome a poor design choice, or a management decision to save half a percent on the materials cost by specifying lower quality materials that'll rust out)Who designed and manufactured the overpriced trash we were producing?
It's the management and the design staff who do that, and from memory they didn't tend to strike as they were getting much better wages.