People can't vote for third parties or independents. Because the system has been rigged so that the major parties are the only ones that can win elections. It would be far better if we adopted a ranked choice voting system that would minimize the ability of parties to control elections.
The system hasn't been "rigged" per se. It's just that that is the system. FPTP leads to two political parties.
In the UK it's Tories v. Labour for example. They do have more than two political parties, mostly because there are regional parties and the make up of the regions often doesn't matter. Scotland has 59 seats, Wales has 40 and Northern Ireland 18
Potentially they can have an impact, Wales and Scotland have plenty of Labour or Tory voting constituencies, NI doesn't and at times the DUP will have to support the Tories to stay in power.
But there hasn't been a non-Labour/Tory PM since Labour became a power in the 1920s....
Proportional Representation is a much better system, ranked choice would probably just lead to the main two parties winning all the time.
For example, Germany votes PR and FPTP at the same time.
PR decides the make up. But the difference can be as much as 10% of people voting differently between PR (for the smaller parties) and FPTP (for the main two parties).
Ireland uses Single Transferable Vote, or ranked choice voting. It does have nine political parties, though only four of them got over 10 seats. However each constituency is between three and five seats... rather than one which is what I think you'd want. For example Carlow-Kilkenny (first alphabetically) has five seats, and the FF gained two seats, and three other parties gained one seat. The guy with 10.3% didn't get elected, but someone with 6.7% did. Because I think it somehow takes into account political party AND candidate. So the party with the most votes may get the most seats.
But the FG with 20.6% of the vote get the same number of seats as the Greens with 5.3%
Not exactly fair.
The Australian also uses this
In the House they use instant run off, which is similar and the main two parties gained 56% of the vote between them.
In the Senate with STV they got about 50% of the vote.
But then the Liberal coalition got 34% of the vote but 42% of the seats
The Labour Party got 30% of the votes and 34% of the seats
So they're getting more than they'd get with PR.