But that's not how the British system works. When you vote in a constituency, it's sometimes inflected by local concerns, but mainly you're voting for the party line, not the individual.
Many political systems work that way. Lots of Americans still vote for the party line in the US as well. Even though technically they are voting for an individual, some Americans just vote for everyone in the Democratic column, or the Republican column, without knowing anything about who they are voting for. This is one of the reasons people complain when ballots aren't readable. People sometimes vote the way they hadn't intended if a candidate's name is in the "wrong" position on the ballot; that is, it's hard to tell which party they belong to. I have seen people do this when I've gone to vote in the US: Walk up to the election worker, ask "Which column is the Democratic column?" and be told "first column on the left" or wherever it is.
Not so much in presidential elections, maybe, but Americans vote by party when voting for the legislature, judgeships, and in local elections. Either way, it's important to know what you are voting for--whether it's a party or a person.
In contrast, the US party platforms aren't that seriously considered.
Not true. See above. Well, I guess it depends on which indvidual does the considering. But certainly a substantial number of Americans care about the party platforms very much.
There's another key difference between the two systems. Only the ruling party can introduce legislation. This differs from the States where the minority party can introduce bills. That's why the US politicians speak about bipartisanship, which is a concept that is ridiculous here. The other thing that matters is ruling party discipline or rebellion. The opposition parties can boo in Commons, but that's about it: they're largely irrelevant. That's why the Tories can only oppose things in the House of Lords.
That just gives more support to the idea that it is important to be able to vote intelligently and sensibly and understand the rules, since the ruling party has that much more power.
In addition, the UK has no separate judicial branch, and the executive branch (monarchy) is pretty much powerless, which makes the legislature even more powerful.