For most of its existence, the WNBA stayed at a fairly fixed size — the same familiar dozen-ish franchises for years at a time. That's changed. New teams have been added, more are coming, and the ripple effects go well beyond just having another city to root against.
The current wave of growth has brought the league into markets that never had a team before — the Golden State Valkyries in the Bay Area, with Toronto (the Tempo) and Portland (the Fire) joining as well. Each new franchise starts from zero: no built-in fanbase, no rivalry history, nothing except a roster and a city willing to show up. Building that from scratch is a bet that women's basketball can draw a crowd anywhere, not just in the league's long-established markets — and so far, expansion franchises have tended to sell out or come close to it in their debut seasons, which is exactly the signal a league wants when it's deciding whether to keep expanding.
Every new franchise means another full roster of paid professional basketball jobs — historically one of the tightest job markets in pro sports, where far more talented players wanted spots than there were roster spots to give them. Expansion doesn't fix that overnight, but it does loosen it: more teams means more players who get to call themselves professionals instead of getting cut in training camp.
Expansion isn't just a basketball decision, it's a business one — and it's happening now because the demand is finally there to justify it. Rising TV audiences, growing attendance, and a wave of new investor interest have made adding a team a much easier sell than it would have been a decade earlier. Every new franchise also comes with an expansion fee paid to the league, which funds the rest of the league's growth in turn.