If you use a mulching mower, you will probably never need to fertilize. I never do.

And March is too early to fertilize in the PNW - May is the recommended time here.

WSU PNW Lawn Care Calendar

btw, If you water once every 7-10 days during the dry summer months you can keep the lawn from going dormant.

It's recommended to put down a spring fertilizer with weed control in the spring. Apply it when forsythia start blooming for optimal results. It won't hurt your lawn. Assuming you follow directions.

Whether or not to fertilize is up to you. I mulch my clippings and if I didn't supplement with fertilizer, my lawn would look bad. If I just spent a lot on sod, I would fertilize.

Lawns don't naturally occur anywhere in nature. You have to do unnatural things, like apply fertilizer, to keep them looking good. What some might consider looking good would never appear in a scotts ad.