Translation:He kept your number and he gave it to me.
Because the people (volunteers) who work on the Irish course don't have control over the website, and the people who work on the website (paid Duolingo staff) don't want to create custom solutions for minority languages that don't use the same tools that the major languages do.
The recent website update created a "one-size-fits-all" web template, so all "Irish to English" exercises display a speaker icon when you are doing a practice. Apparently the actual discussion pages haven't been updated yet (they still have the old notification code) so the speaker icon is only displayed if there is actual audio available. It's possible that the Duolingo engineers might tweak the new website code for Irish at some point in the future, but it's far more likely that they'll find other things to do instead (like maybe getting notifications working properly, or allowing comments on exercises that don't already have comments).
I detect a note of frustration and irritation here! I do apologise for that. I know what it's like trying to work when you are short of resources and some way down from the top of the priority tree. However, to offer something constructive, the Irish government is very supportive of things which support and promote the language. They are aware of Duolingo,, as shown by the presence of their president when Duolingo Irish was celebrating its 2 millionth student. After all, that's about 25 times the total population of native speakers of Irish in Ireland. I just think that an approach to the Irish Government could get you some resources. Try an approach to the Department of Arts, Heritage, Rural and Gaeltacht Affairs. If you'd like me to help, send me a private email. Good luck!
Duolingo isn't a software contractor looking for private commissions to make ends meet. They have a product that they have a particular vision for, and diverting resources away from that vision to suit the needs of one particular subgroup of users isn't likely to happen, even if those resources were fully funded by a 3rd party. If the Irish government wants to write Duolingo a cheque, I'm sure it wouldn't be refused, but if it comes with caveats and conditions, it'd have to be far more substantial than anything that's likely to be available.
I have no direct or indirect connection with Duolingo, I'm just observing the nature of the changes that Duolingo has made over the last couple of years, and the rate at which those changes have happened. Duolingo devoted considerable additional resources to the initial development of Irish as a non-TTS language, and then devoted even more resources to Irish to respond to issues with the initial speaker for the Irish audio, but those changes took over 18 months to implement. According to the notes in the incubator, the volunteer contributors are now working on a substantial reworking of the Irish course, which will probably require substantial support from Duolingo staff to roll out once the teaching content is ready.
It's been months since Duolingo started to trial the new webpages, and it still hasn't prioritized some pretty fundamental issues like the ones mentioned above. I have no idea if this is because app development takes precedence over website development, or because a decision has been made to leave well enough alone, or because other changes are being made behind the scenes to support other features, or even if the changes have already been made, but are being A/B tested to see if they make any difference. But based on past performance, it doesn't seem very likely that such an inconsequential change will be made to the Duolingo web code, even if it's something that could be knocked out in an afternoon
You asked "If it doesn't have audio, why not remove the audio symbol?" I provided some background, based on my own observations, but the basic answer is that Duolingo doesn't appear to believe it is worth the effort. It's possible that it's the kind of change that might get greater visibility during the window when the Duolingo staff start whatever process they go through when they start to implement whatever major curriculum changes the volunteer contributors are currently working on, but for now, it isn't even on the Duolingo developers' radar as an issue.