A few days ago Google announced that the Keyword Planner will show only limited data to the adverstisers with low monthly spend. However no reason was given for it.
Finally Google has come up with an answer to the question in a Google AdWords Help thread. Google’s CassieH said, that this move was made to to prevent bots and other services from abusing the intended use of Keyword Planner.
“This change was made so that we can consistently give advertisers the data they need to optimize their accounts, while preventing "bots" and other services from abusing the intended use of Keyword Planner. The search volume estimates, though displayed differently in some cases, still provide an accurate and helpful view of how many clicks and impressions keywords may receive.”Google Clears The Air On Keyword Planner Updates!,