Even after the new SSA back end, they can still be large.
Take if from a long time compiler write who has nearly 30 years experience working with SSA: SSA is no panacea. It is a representation that makes some optimizations easier to express and sometimes more effective. Many of the optimizations that SSA facilitates tend to raise register pressure. I can be a very delicate balancing act.
Optimizing for size is a dark art. Most compiler projects invest relatively little effort in that direction.