It is not wise to create, for something that is desirable, a dependency which is undesirable.
One example is using tobacco taxes to pay for children's healthcare. It sounds good politically, but then you're dependent on smoking and it's a conflict of interest to get people to stop smoking.
Another example is when law enforcement agencies find they are dependent on fines from speeding, or assets confiscated from drug dealers. If people stop speeding, or drugs stop coming through the area, which is what they say they want, they'll have a budget crisis. So there's a conflict of interest.
The example at hand -- heating living space with excess heat from data centers -- is not as controversial. You could argue that there's no particular need to make computers run cooler. But there certainly has been, and continues to be, a lot of research in that area. The potential conflict is enough to fall back on what we have learned -- or in some cases, not yet learned -- from other conflicted dependencies.