To merge or not to merge, that is the question

I don't normally peruse Liblogs, but this one that I caught on Full Comment actually makes a lot of sense.

It leads to a few questions, but what it comes down to is why DON'T the Liberals discuss merging to the right rather than the left? Why do they insist on moving further away from the centre of the political spectrum rather than towards it?

It's a common myth being perpetuated that Canada is a centre-left country. I would disagree with that assessment. The only evidence is that people vote for the NDP, the Bloc and the Green Parties, all of them farther to the left of the Liberals, but the only thing skewing things is that the Liberal Party, which has campaigned on the left and governed from the right in the last 25 years is a centrist party. Canada is no more a centre-left country than it is centre right, but it votes for the party that is closest to the centre as it can. Right now, this is the Conservative Party, but historically it has been the Liberal Party (and the Progressive Conservative Party) which has occupied that space.

In short, it would make sense for the Liberal Party to merge with the Conservatives - the true lefties will drop off and find their space to occupy in the other 3 parties. The question that I would have is this:

Why would the Conservatives want to merge with the Liberals?