In my case I had 350 mainly to get a decent upload speed, which was 35, I was paying £34 a month.
The April price rise came round, and it was going to increase my monthly charge to £37 a month.
I then accepted an upgrade offer to the 500 package, which increased my monthly cost to £36.24, and no price rise until April 2025, so slightly cheaper and much faster, and with a 50 Mbps upload.
I then logged in to remove marketing permissions, and noticed an upgrade offer for 1 Gig for £40, an increase of £3.74, well for that small amount it would be rude not to, and I also get a nice increase in my upload to 100 Mbps.
Do I really need 1 Gig, no not really, it just a nice to have, and nice to have a better upload speed.
My brother has 1 Gig symmetrical, much cheaper as well, but he uses a VPN between his house and his partners, so the faster speeds really do help.
There's many other reasons, downloading software quicker, uploading to cloud back up etc, it really depends what you use you connection for.