Like the other comment, they may not want to grow that fast. You can only produce so much revenue over a given period. This may be their ceiling and they can afford to incrementally increase clients through other routes at a more controllable rate. Unless you could figure an exact amount they could increase ad spend by to get X clients (I wouldn’t try to do this though).
Another point could be that they are cautious of running through the total potential of new clients from digital ads and would rather have stable and forecastable revenue than a huge influx In a shorter period that wanes. Since it’s a business, it still has costs that need revenue to support even when business is slow.
Just change the logo my friend. No one is buying your product because of the recognition they get from the logo. You see huge retailers with recognizable products even has the offer styles without their logo to encourage additional sales.
If you’re that concerned about it, put an extra page on your website or expand on your about us / mission statement and talk about this future branding.