.......... so what is the point in joining? Convince me.
1) Calculate what an IR investigation would cost you in time, non tax deductible accountancy fees, aggro, and stress. These still apply even to the totally innocent.
2) Shop around for an insurance policy quotation against 1) occurring.
3) Add in free business banking (if you want it).
4) Add in a legal helpline (again, if you want it - you never know what may crop up).
5) There is also access to various meetings/seminars where it may be possible to mingle and promote your business to other businesses. This usually costs a bit extra though on a per meeting basis (often with food thrown in).
6) When WFP companies in the southeast were faced with extinction during the drought a few years ago, the FSB was the most powerful voice behind the scenes lobbying in the places where it matters. It will never be known for certain how much their efforts delayed the banning of WFP (and cerain other businesses) until the rain came and prevented the scenario. I would agree that non members would have benefitted equally from this but to make such representations does cost money.
7) The FSB fee is tax deductible so effectively costs about 28% less than the gross figure (the tax saving is more for higher tax payers).

You get a free magazine once in a while. Occasionally there is actually something of interest in it.
9) Access to a website - subject to providing your membership card number.
10) I suppose that usage of their logo on stationery might swing getting a particular type of job. Although there is no prior vetting of members, the fact that someone has taken the trouble to join such an organisation can give the impression that they are not a transient company. That can sometimes be quite important in a trade that has a here today/gone tomorrow reputation.
I regard it as an insurance policy in the main - but one where I don't actually feel ripped off. I did have cause to phone the legal helpline on one occasion but the situation was resolved without needing them in the end.
My membership costs me £100 a year. The first year was higher as there is a setup fee - possibly some of that fee went to the guy who visited me. There genuinely is no hard sell about this.
The only down side I have encountered is that sometimes other members phone you on telesales calls. This is very unusual though (perhaps 8 calls in 3 years). Some of them make it sound like they ARE the FSB rather than being honest that they are just members. I always question it now when they say they are from the FSB because, without fail, they then admit that they are just members. I feel this is sharp practice but no fault of the FSB itself.
I'm not trying to convince you to join. I'm not bothered one way or t'other. But you did ask why people join it.