Ideally, and traditionally, religious work should be done first and foremost as a service to Allah. It doesn't not mean that one cannot be paid for it, but just that money shouldn't be the main goal. If someone's main goal is money, there are other professions which are more lucrative.
Religious work - like art or sports or other endeavors which require a lot of dedication - has the highest quality when it is done out of sincerity and love for what one is doing. When it is done primarily for financial gain, it loses something. Also, when it is done with money as the priority, the speaker or reciter loses their freedom to speak the truth as they see it and can begin to feel compelled to please the people rather than please the Truth.
There have been some notable scholars throughout history who took no money for their efforts.
However, on the flip side, it is good for communities to assist those who serve them financially. When a community hears a speech or majlis, they only see the hour or two of the program. However, the person delivering it may have had to take time off of paid work to prepare or travel, invest time and money in training and books and developing speaking skills, etc, etc. For instance, if someone takes 2 weeks off of work to travel to give majalis, they are losing a lot of their basic income.
Some people also rely on lectures and majalis for their income, especially because sometimes people who work full-time in the religious community are not in a good financial situation. Often it is the people who are the most reliant on receiving hediyas that are shy to ask for high amounts or specific amounts. So it is good to be thoughtful of that and to be generous within the range of what is possible.