They sell them after 3 years because thats when the finance ends or lease,you can write it all off in year 1 I’ve done it,if you want to put a big amount against your Tax it gives you a breather from paying it the following year but you will get a larger bill the next time round.
I did it some years ago claimed 100% and I purchased the van for cash brand new I had a terrible accountant about 18 months 2 years later I had a 15 grand Tax bill,10 in the January 5 in the July this was about 10-11 years ago went away over Xmas spent a fortune and got this update about my Tax on about the 10th of that January due to the oversight lol,like I say terrible accounting.