I voted "Yes". However, that's for me. I commute to work most days a week, so those days my route is pretty much identical. I could vary the route, but haven't to this point. I am planning on varying my ride in, as I have more time to do that. My ride home however is pretty much locked in, as it's the fastest route, and I need to be home in the least amount of time possible after work.
For me, if that's all I was doing, I would (and am) continue to get faster on my commute, but wouldn't be challenged in other ways (climbing, endurance, etc.). I know I can vary the intensity on my ride, and I do do that, but for me at least it's not the same as doing significantly different lengths. I love my long rides on weekends, and even really short rides with my kids. Change keeps things fresh for me. Additionally, I'm a very goal/performance oriented person, and I find setting different sorts of goals for myself, such as a certain distance, or average speed on my commute to be very rewarding.
I started riding 4 months ago, and commuting regularly 3 months ago. My commute is 14.5km (each way), with about 350' of climbing (ironically each way as well, my house and work are almost identical elevations). My first goal was to average 30km/h, which I achieved a month or two in. My current goal is to average 20mph (32.2km/h). 31.3km/h is my best so far, so still some work to do there. I need goals like that to keep the same route every day fresh.
I also set a goal to do a metric century, and did that last month (120.2km). I went significantly over as I hit a major detour I wasn't expecting on my route. However, I certainly realized then that I had it in me to do my next goal, an imperial century. I hope to do that by the end of October.
Anyway, that's my perspective, and what works for me. What works for someone else may very well be entirely different. I know that my wife hates monitoring performance to that extent!