Why? My voting strategy is just basic boolean logic. Nothing fantastical at all. I am firmly opposed to elite Tory minority rule, but I believe in democratic reform, transparency, accountability, human rights/civil liberties, a fair tax progressive economy etc (none of which being Labour priorities). I can best achieve this change under the existing system by voting for more progressive and democratic alternatives to Labour anywhere aside from a Lab/Tory marginal.
You should vote the way you want to (obviously), but it's the minority position. If things are to change, one of the two main parties will have to do the heavy lifting (PR or a progressive alliance of some sort) and I'm not seeing any signs of that at the moment. One interesting 2024 election scenario is the SNP holding sway in Parliament. That might lead to some form of re-direction.