When talking with other people in the field of IT, I often come across people whose employers won't pay for conferences, and sometimes even won't let them take time of to go there.
I have in the past tried to make the case for allowing employees to go to conferences, but I think it is time to also acknowledge and address the dangers of allowing employees to go to conferences.
The rest of this post will list the major explanations I've heard, and try to address them.
1. The company only work with legacy systems, and all the new stuff mentioned at the conferences is irrelevant for us.
A conference like GOTO doesn't only present new languages and technology, but also have sessions on methods, architecture and many other things that are several layers of abstraction away from actually systems development.
Even if your company doesn't make use of the newest technology, conferences present a rich source for re-evaluating current practices, and address inefficiencies in the current setup. Many, if not all, of the speakers have not only worked on cutting edge greenfield projects, but also on brown-field projects, that have turned into big balls of mud, so they understand the need for taking such projects into account.
2. When my employee go to a conference, they will met people from other companies, and be tempted to go there.
There is an old anecdote about a the leaders of a company talking to a consultant, and asking "what if we train our employees, and they all leave?" To which the consultant answers, "what if you don't train them, and they stay?".
If you are afraid that the employees will leave if they hear about conditions at other companies, maybe you should address the conditions at your company, rather than letting them get worse, by not allowing people to go to conferences.
Also, have you considered the idea that the employee might convince other people to check out your place as a potential workplace?
3. If I allow one employee to go to a conference, everyone wants to go.
First of all, I don't think that is true. In most companies, there is a large group of employees who don't particularly like going to conferences, and thus won't ask for it.
But even if that's the case, then I don't really think it is a problem. There might be an economic limit to how many can go, but that can probably be solved by creating a turnus, where employees get to go on alternate years.
If a large group of employees go, then they can either use the conference as a team event (if they work together), or as a way to get to know people in other parts of the organization better (if they don't work together). Either way, it makes for a closer knit mass of employees.
4. Conferences are expensive
"Expensive" is relative. IT employees are usually highly paid, and hard to recruit. For many good IT people, conferences are a factor when considering whether to stay or change jobs.
If someone changes jobs, the cost of replacing that person is much, much higher than the cost of allowing them to go to a conference.
5. My employees will get frustrated over hearing about new tech that they can't use
Yes, this is a real risk, but there are ways around that. Maybe allowing them to slowly introduce new tech in their current projects, or by allowing them some "play time" to build tools and other programs that can help them in their daily life.
Trying to keep them away from learning new tech is only going to work for the most incurious of employees. If you are fine with your employees not wanting to keep up to date on their field, that is fine, but if that's not the case, then you have to find a different solution than keeping them from konferences.
6. My employees will try to implement the newest fad after the conference
Somewhat related to point 5. Yes, this is a risk, but you can limit the risk by ensuring that the employee get an outlet for their creativity.