It may seem silly to you, but you have to remember that airlines make money out of selling different levels of flexibility and different kinds of tickets to their passengers.

They can't just then turn around and let anyone with an inflexible ticket make changes as the pax wishes (or, with a semi-flexible or flexible ticket, unilaterally make changes without first advising the airline including paying change fees where necessary).

Ultimately, everyone gets the same seat on the same plane, but the tickets are all different.

Your onward flight sectors will be cancelled if you skip any part of the ticket. You also face the prospect of being billed for the journey you actually flew - and one-way tickets are often priced surprisingly high, particularly when "bought" on the day of travel!

If you really must leave the plane at this point, then you must do whatever you can in advance to change your ticket to allow this.

Some people may recommend feigning illness or some other calamity that would perhaps persuade the staff to deboard you there, but this would then likely involve the crew determining whether it was better to deboard you or let you continue your journey [where better facilities to treat the illness may be available], and any deboarding would then require you to seek medical assistance with the airline/airport's staff looking after you there - and you would have to stick around so that the ticket desk could rebook you on the next available/suitable flight and make sure your ticket isn't automatically cancelled - so certainly not a situation that simply allows you to slink off and do whatever you have to do. Don't lie to the airline!

If it really is an urgent business meeting, then get your employer/client (or yourself, if you work for yourself!) to buy new tickets to cover this change of plans.