As almost everyone has been to school and/or has children, they perceive that they know how easy the job is. What they forget is that some of the 30 people in the room that teachers are expected to teach are just not in a position to be able to learn, or are actively trying to stop the teacher from teaching. This is perceived as being the teacher's fault, and they are penalised financially for it. Observations have to be recorded, assessments moderated, teaching observed and scrutinised by SLT, advisors and inspectors.
Where pupils have any kind of additional needs, schools are the gateway to getting additional support. Except that support isn't there due to the overwhelming demand, so the teacher has to provide what they can. Despite being a professional with relevant qualifications, a recommendation as to what a child needs, can only be considered if it is supported by external evidence.
The Safeguarding responsibility is huge. A child is absent yet again. Have they just got another bug, or are they being kept home until their bruises have faded or so they don't mention xyz that happened at the weekend?
Parents refuse to engage with school's requests or become aggressive. Are they hiding something that means the child isn’t safe?
No PE kit again. Is it just forgotten? Chaotic household? No washing facilities so PE kit or underwear isn't clean? Scars from unexplained injuries that might be seen when getting changed? etc.etc. etc.
Every interaction with every child or parent has the potential to be misinterpreted, and result in a potentially career-ending allegation. Read some posts on here about things some people want to complain about and how upset they get about it. Schools are the only agency that most families have to interact with every day. When life gets stressful, it is often the school that picks up of the difficulties or that people turn to, either for support or to sound-off at.
Listen to the news over a period of a few days. Every time an issue comes up that politicians can not solve, the expectation is that the teaching profession will. With no extra resources or training.
Teenage pregnancy, drugs, knife crime, forced marriage, child poverty, healthy eating, safeguarding, mental health, road safety...
When comparing the pay to that of other jobs, remember that many teachers are providing resources out of their salary in order just to do their job. Things like supplying extra pens and glue sticks, by printing resources at home using their own ink, paper and electricity, by bringing in interesting resources, or by spending money at the school fair.
If there was ever an all-out total continuous teachers' strike, it wouldn’t be long before other services were affected to breaking point, either by having staff unable to work as they need to care for their children or by having to deal with the additional fallout created by there being large numbers of under-supervised children and teenagers.