It's something I truly don't understand.
Why do mechanics feel the need to slap their ugly-arse sticker on my car after doing a job I've paid them to undertake? Let's think about this for a moment:
I've come to you already
I don't need to know who you are anymore, you don't need to market to me - I'm already there. So why would you think slapping a sticker on my car will help? If you did a good job, it'll stand out in a sea of mediocre and I'll be back. If you did poorly, that sticker will just be a constant reminder of how annoyed I am.
Either way - it's not doing you any favours.
Other drivers can't see the bloody thing
Unless your phone number is bigger than the logo, other drivers can't see anything actionable on standard mechanic's sticker. So even if the sticker made it past the "Meh" filter and attracted some minimum level of attention, it's not building business for you. It's just sitting out there, fading in the hot Australian sun and being generally crappy and mediocre.
After cinema advertising, this is just about the most useless form of marketing known to man.
The car it's on doesn't exactly recommend your business
Why on earth would you even want your sticker on a rusted out 1980's Datsun? Apart from perhaps the micracle that it's running at all, it's not exactly a shining testament to your business that it's associated with the worst car most people will see on their daily commute.
Let's face it. Mechanics usually aren't known for their subtlety. Your stickers are red, black, neon green, brushed metal texture or some combination of all of the above.
That does not sit nicely with my champagne coloured Kluger. Or any other car for that matter.
You're operating on autopilot
This is probably the most damning statement of all.
These days the businesses that succeed are those that provide superior customer interactions. Yes, the product itself needs to be solid, but it's the experience that stays with us.
If your entire customer outreach effort is to vandalise their car, then you've got more problems than that crappy sticker has a hope of fixing.