For me, being fresh out of university, I didn't really think to press on salary too much and was just happy to land a job. In my first job, I recall not knowing the salary until I got the contract and offer (luckily, it was surprisingly above average pay).
When I moved into the software industry, I started to realise my worth a bit more and job-hopped for 10-50% pay bumps on an annual basis for the first few years and just started chasing higher salaries and turning down interviews unless they were in my desired range.
I know many other engineers who never changed this behaviour (or were never taught to be more ruthless and know their worth) and were just happy to receive any increase in salary - and as a result had 10+ years in the industry and had utterly pitiful salaries due to their employer simply taking advantage - you'll never receive the same increase in pay by remaining loyal to a company versus job hopping. I'm not sure if it's a cultural thing in the UK or what but this is the type of advice that should be given in schools more IMO.