It's as easy as saying like "I just got an offer from $competitor".
The process may take months because candidates usually ask for time to prepare, and some latency once the offer is accepted (background check, etc). If you are actively looking for a job, you are most likely already prepared.
That’s still terrible by industry standards. We lost many candidates because they did have competing offers and couldn’t sit on them for a month while the hiring committee waited until the next blood moon to gather.
I'm sure there are plenty of candidates giving up because they received a competing offer and wouldn't wait, but I think it's reasonable to expect a hiring process to take a month, even in small companies.
Edit: I also have anecdotal evidence of cases where an offer would be made withing 2-3 business days after the interviews at both Google a Facebook.
Yes. It’s fucking terrible. That pace isn’t acceptable for things with significantly more at stake (buying a house, getting married, donating an organ). Google just abused its position as a desirable place to work while I was there to take time to hire candidates.
Do you want to optimize to hire people who accept whatever offer comes first? Isn't it worth waiting a couple weeks to get the right job that you will spend the next few years of your life at?