AdWords gives you limited characters to get your message across in an ad. You want to use the characters available in the best possible manner. Very often, this mean foregoing punctuation in ad text. Earlier, it was not important to add punctuation in ad text because you were not following grammar rules. However, now it has become almost imperative to do so.
Google keeps trying new ways of showing ads in the top positions above the search results. Sometimes the description line 1 is moved up to show with the headline, sometimes Description line 2 is moved up to show with description line 1. In the first case, Google adds a hyphen between the headline and description line 1. However, in the second case it just moves the description line 2 up. So, if the description lines don’t have punctuation or conjunctions then it appears as one long sentence which doesn’t make sense to the user when they read it.
If the user doesn’t understand the text in your ad he/she will just move to the next ad. Your ad is showing in the most coveted position on the search page but you lose out because you didn’t use a full-stop or comma. In the long run, this will affect ad performance because the ad will accrue impressions but few clicks which means a low clickthrough rate (CTR).
Next time when writing ad text, don’t eliminate the comma or full-stop.