Because the fountain of evil in modern democracy is the first past the post electoral system. The natural outcome of FPTP is a 2 party system that can be as dysfunctional as possible yet still garner roughly half the votes. Any third party that fields candidates with more favorable manifesto will just sit the vote, effectively giving the vote to the opposing party. This means that in FPTP you’re invented to vote for the least worst party rather than the party that most aligns to your views.

Here’s a playlist all about electoral systems: youtube.com/playlist?list=PLej2SlXPEd37YwwEY7mm0W…