Because it's fun.
Simply put if Quebec is gone, so are 35-45 safe liberal seats. If Alberta is gone, so is about 32 safe conservative seats. That has an impact. I don't know why people are struggling with this.
Re: Quebec. It also provides 35-45 safe seats for the other parties, so its a wash for the Liberal Party. I'll post the numbers, since you appear to be struggling with this:
Election Year: LPC % of total seats / LPC % of total seats excluding Quebec
1993 (LPC majority): 60%/72%
1997 (LPC majority): 52%/57%
2000 (LPC majority): 57%/60%
2004 (LPC minority): 44%/49%
2006: (CPC minority) 40%/48%
2008: (CPC minority) 46%/55%
2011: (CPC majority) 11%/12%
2015: (LPC majority) 54%/55%
2019: (LPC minority) 46%/47%
2021: (LPC minority) 47%/48%
2025: (LPC minority) 49%/47%
So, in every election for the last 35 years, the LPC share of seats would have been larger if Quebec was excluded (save 2025, but the difference is pretty small). In most years, the outcome would have been the same but in some years, the difference is dramatic (1993, 1997, 2004) and in 2008, the absence of Quebec would likely have flipped the result from a Conservative minority to a Liberal majority.
So, you've claimed Quebec props up the Liberal Party and that "they would never be the natural governing party again" if the province left. But based on seat math, this is categorically false as Quebec is largely a wash for a healthy Liberal Party. Your argument is hyperbole.
Now, turning to Alberta, it is clearly a stronghold for the CPC, and they would be toothless without it. But considering the Liberals have traditionally been a federalist party, and it still garners 30% of the vote share in the province, your statement that the LPC would be happy to see the province go seems specious at best.