Most don't want any of the options presented to them. Almost all the parties don't really serve the electorate, so a large number of people are abstaining.
I appreciate this in an anecdotal but I've spoken to quite a few people I know in my family, that saw it as their civil duty to vote and they told all told me some variation of "there is nobody worth voting for", "I don't think it matters who I vote for".
The UK is FPTP. Reform split the previously unified conservative vote so labour won with a historically low %.
There are good options I think for most people. I did not like labors party policy, so I voted for the Lib Dems in a large labour area, did it achieve anything for them? No, did I do my civil duty?
I am sure many green voters felt the same way for many years and now they stand a decent chance of getting many seats!